Merge branch 'master' of http://182.92.203.7:2001/r/testbookLayout
| | |
| | | VUE_APP_ENV = 'product' |
| | | VUE_APP_API_URL = "https://jsek.bnuic.com" |
| | | # VUE_APP_RESOURCE_CTX = 'https://jsek.bnuic.com/books/resource/' |
| | | # VUE_APP_PUBLIC_PATH = 'https://jsek.bnuic.com/books/book/botany' |
| | | VUE_APP_RESOURCE_CTX = 'http://182.92.203.7:3007/books/resource/' |
| | | VUE_APP_PUBLIC_PATH = 'http://182.92.203.7:3007/books/book/botany' |
| | | VUE_APP_RESOURCE_CTX = 'https://jsek.bnuic.com/books/resource/' |
| | | VUE_APP_PUBLIC_PATH = 'https://jsek.bnuic.com/books/book/mathBook' |
| | | # VUE_APP_RESOURCE_CTX = 'http://182.92.203.7:3007/books/resource/' |
| | | # VUE_APP_PUBLIC_PATH = 'http://182.92.203.7:3007/books/book/botany' |
| | | VUE_APP_BOOK_LIST = "childHealth/lifeCare/sportsAndHealth/embedded/english/artAndDance/artAndDrama/mathBook/botany" |
| | | VUE_APP_BOOK_ID = 'botany' |
| | | VUE_APP_BOOK_ID = 'mathBook' |
| | |
| | | // artAndDrama |
| | | // mathBook |
| | | // civilAviation |
| | | |
| | | this.activeBook = await this.config.getBookConfig( |
| | | process.env.VUE_APP_RESOURCE_CTX + |
| | | (process.env.VUE_APP_ENV == "product" |
| | | ? process.env.VUE_APP_BOOK_ID |
| | | : "civilAviation") |
| | | : "mathBook") |
| | | ); |
| | | |
| | | // this.activeBook = await this.config.getBookConfig( |
| | |
| | | // 默认加载章节 |
| | | this.showCatalogList = [1]; |
| | | // 滚动监听节流 |
| | | debugger |
| | | this.throttledScrollHandler = _.throttle( |
| | | this.scrollFun, |
| | | this.throttleThreshold, |
| | |
| | | scrollFun(event) { |
| | | this.handleVideoPicture() |
| | | // 判断向上滚动还是向下滚动 |
| | | console.log(11); |
| | | |
| | | if (event.target.scrollTop > this.previousScrollTop) { |
| | | this.getAduio(); |
| | | // 向下 |
| | |
| | | currentScrollTop >= |
| | | event.target.scrollHeight - this.loadThreshold |
| | | ) { |
| | | console.log(1); |
| | | |
| | | debugger |
| | | // 到达阈值 |
| | | if ( |
| | | this.showCatalogList[this.showCatalogList.length - 1] < |
| | |
| | | .page-box { |
| | | position: relative; |
| | | box-sizing: border-box; |
| | | min-height: 1150px; |
| | | min-height: 1120px; |
| | | margin-bottom: 20px; |
| | | box-shadow: 0 3px 6px 1px #00000029; |
| | | background-color: #fff; |
| | |
| | | .t0 { |
| | | text-indent: 0; |
| | | } |
| | | .t1 { |
| | | text-indent: 1em; |
| | | } |
| | | .t- { |
| | | text-indent: 0.5em; |
| | | } |
| | |
| | | } |
| | | .page-box { |
| | | box-sizing: border-box; |
| | | min-height: 1150px; |
| | | min-height: 1120px; |
| | | margin-bottom: 20px; |
| | | box-shadow: 0 3px 6px 1px #00000029; |
| | | background-color: #fff; |
| | |
| | | } |
| | | .mt-40 { |
| | | margin-top: 40px; |
| | | } |
| | | .mt-60 { |
| | | margin-top: 60px !important; |
| | | } |
| | | .mt-80 { |
| | | margin-top: 80px !important; |
| | |
| | | height: 0 !important; |
| | | box-shadow: none !important; |
| | | } |
| | | // 带按钮p标签 |
| | | .p-btn { |
| | | display: flex; |
| | | justify-content: left; |
| | | align-items: center; |
| | | flex-wrap: wrap; |
| | | i { |
| | | text-indent: 0; |
| | | } |
| | | } |
| | | .iframe-box { |
| | | width: 100%; |
| | | min-height: 800px; |
| | | border: 1px solid #00a1e9; |
| | | border-radius: 10px; |
| | | } |
| | | } |
| | | |
| | | /* 媒体查询做基础响应式布局 */ |
| | |
| | | <template> |
| | | <div class="chapter" num="1"> |
| | | <div class="chapter" num="2"> |
| | | <div class="page-box" page="8"> |
| | | <div v-if="showPageList.indexOf(8) > -1"> |
| | | <h1 id="a007"> |
| | |
| | | </p> |
| | | <p>(2) 0~10中的所有奇数;</p> |
| | | <p>(3) 我国农历二十四节气;</p> |
| | | <p>(4) 方程x2-5x-6=0的解;</p> |
| | | <p>(4) 方程<i>x</i><sup>2</sup>-5<i>x</i>-6=0的解;</p> |
| | | <p>(5) 到一个角的两边距离相等的所有点.</p> |
| | | |
| | | <p class="left"> |
| | |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <div class="center openImgBox"> |
| | | <img class="img-c" alt="" src="../../assets/images/0023-1.jpg" style="margin-top: 30px" /> |
| | | <img class="img-b" alt="" src="../../assets/images/0023-1.jpg" style="margin-top: 30px" /> |
| | | <p class="img" style="font-size: 14px">图1-4</p> |
| | | </div> |
| | | |
| | | <p>根据子集的定义,任何一个集合A都是它自身的子集,即A⊆A.</p> |
| | | <p> |
| | | 我们规定:<b>空集是任何集合的子集</b> |
| | | ,即对于任何一个集合A,都有∅⊆A. |
| | | </p> |
| | | |
| | | <div class="img-float openImgBox"> |
| | | <img class="img-c" alt="" src="../../assets/images/0023-2.jpg" /> |
| | | <p class="img" style="font-size: 14px">图1-5</p> |
| | |
| | | </p> |
| | | </li> |
| | | </ul> |
| | | |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"> |
| | |
| | | <!-- 030 --> |
| | | <div class="page-box hidePage" page="37"> |
| | | </div> |
| | | |
| | | <!-- 函数控件弹窗 --> |
| | | <el-dialog :visible.sync="dialogVisible" width="60%" :append-to-body="true" :show-close="false"> |
| | | <div slot="title" style="padding: 0 0 15px 0; position: relative"> |
| | | <svg style="position: absolute; right: 10px; cursor: pointer" @click="dialogVisible = false" t="1718596022986" |
| | | class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="4252" width="20" |
| | | height="20" xmlns:xlink="http://www.w3.org/1999/xlink"> |
| | | <path |
| | | d="M176.661601 817.172881C168.472798 825.644055 168.701706 839.149636 177.172881 847.338438 185.644056 855.527241 199.149636 855.298332 207.338438 846.827157L826.005105 206.827157C834.193907 198.355983 833.964998 184.850403 825.493824 176.661601 817.02265 168.472798 803.517069 168.701706 795.328267 177.172881L176.661601 817.172881Z" |
| | | fill="#979797" p-id="4253"></path> |
| | | <path |
| | | d="M795.328267 846.827157C803.517069 855.298332 817.02265 855.527241 825.493824 847.338438 833.964998 839.149636 834.193907 825.644055 826.005105 817.172881L207.338438 177.172881C199.149636 168.701706 185.644056 168.472798 177.172881 176.661601 168.701706 184.850403 168.472798 198.355983 176.661601 206.827157L795.328267 846.827157Z" |
| | | fill="#979797" p-id="4254"></path> |
| | | </svg> |
| | | </div> |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" style="width: 100%; min-height: 800px"></iframe> |
| | | </el-dialog> |
| | | |
| | | <!-- 解题思路弹窗 --> |
| | | <el-dialog :visible.sync="thinkingDialog" width="40%" :append-to-body="true" :show-close="false" @close="closeDialog" class="thinkDialog" > |
| | | <div slot="title" class="think-header" style="padding: 0; text-align: center; color: #333;display:flex;justify-content: center;"> |
| | |
| | | }, |
| | | collectImg: require('../../assets/images/icon/heart.png'), |
| | | collectCheck: require('../../assets/images/icon/heart-check.png'), |
| | | dialogVisible: false, |
| | | thinkingDialog: false, |
| | | videoPath: '', |
| | | stepIndex: 1, |
| | |
| | | <template> |
| | | <div class="chapter" num="2"> |
| | | <div class="chapter" num="3"> |
| | | <!-- 第二单元首页 --> |
| | | <div class="page-box" page="38"> |
| | | <div v-if="showPageList.indexOf(38) > -1"> |
| | |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 已知<i>a</i>><i>b</i>>0. |
| | | </p> |
| | | <p>(1) 比较2<i>a</i>与2<i>b</i>的大小;</p> |
| | | <p>(2) 比较-2<i>a</i>与-2<i>b</i>的大小;</p> |
| | | <p>(3) 比较<i>ac</i>与<i>bc</i>的大小.</p> |
| | | <p> |
| | | <p class="p-btn"> |
| | | (1) 比较2a与2b的大小; |
| | | <span class="btn-box" @click="isShowAnswer0 = !isShowAnswer0"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p v-if="isShowAnswer0"> |
| | | <span class="zt-ls"><b>解</b></span>(1) 因为<i>a</i>><i>b</i>,2>0,根据性质2,有2<i>a</i>>2<i>b</i>. |
| | | </p> |
| | | <p> |
| | | <p class="p-btn"> |
| | | (2) 比较-2a与-2b的大小; |
| | | <span class="btn-box" @click="isShowAnswer1 = !isShowAnswer1"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p v-if="isShowAnswer1"> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | (2) |
| | | 因为<i>a</i>><i>b</i>,-2<0,根据性质3,有-2<i>a</i><-2<i>b</i>. |
| | | </p> |
| | | <p>(3) 若<i>c</i>>0,根据性质2,有<i>ac</i>><i>bc</i>.</p> |
| | | <p>若<i>c</i><0,根据性质3,有<i>ac</i><<i>bc</i>.</p> |
| | | <p>若<i>c</i>=0,则有<i>ac</i>=<i>bc</i>=0,所以<i>ac</i>=<i>bc</i>.</p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 已知<i>a</i>><i>b</i>,比较<i>a</i>-1与<i>b</i>-2的大小. |
| | | <p class="p-btn"> |
| | | (3) 比较ac与bc的大小. |
| | | <span class="btn-box" @click="isShowAnswer2 = !isShowAnswer2"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 因为<i>a</i>><i>b</i>,-1>-2, |
| | | <div v-if="isShowAnswer2"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | (3) 若<i>c</i>>0,根据性质2,有<i>ac</i>><i>bc</i>. |
| | | </p> |
| | | <p>若<i>c</i><0,根据性质3,有<i>ac</i><<i>bc</i>.</p> |
| | | <p>若<i>c</i>=0,则有<i>ac</i>=<i>bc</i>=0,所以<i>ac</i>=<i>bc</i>.</p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | <span class="zt-ls"><b>例2</b></span> |
| | | <span class="t1">已知a>b,比较a-1与b-2的大小.</span> |
| | | <span class="btn-box" @click="isShowAnswer3 = !isShowAnswer3"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p>根据推论1,有<i>a</i>+(-1)><i>b</i>+(-2),</p> |
| | | <p>即<i>a</i>-1><i>b</i>-2.</p> |
| | | <div v-if="isShowAnswer3"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 因为<i>a</i>><i>b</i>,-1>-2, |
| | | </p> |
| | | <p>根据推论1,有<i>a</i>+(-1)><i>b</i>+(-2),</p> |
| | | <p>即<i>a</i>-1><i>b</i>-2.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <p> |
| | | 因为(<i>a</i><sup>2</sup>+1)-2<i>a</i>=<i>a</i><sup>2</sup>-2<i>a</i>+1=(<i>a</i>-1)<sup>2</sup>,且当<i>a</i>≠1时,(<i>a</i>-1)<sup>2</sup>>0,所以<i>a</i><sup>2</sup>+1>2<i>a</i>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 分析本节“问题提出”中的问题. |
| | | <p class="p-btn"> |
| | | <span class="zt-ls"><b>例1</b></span> |
| | | <span class="t1">分析本节“问题提出”中的问题.</span> |
| | | <span class="btn-box" @click="isShowAnswer4 = !isShowAnswer4"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 作差可得<math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <div v-if="isShowAnswer4"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 作差可得<math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mo>+</mo> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>166</mn> |
| | | <mo>+</mo> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>106</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>98</mn> |
| | | <mo>+</mo> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>166</mn> |
| | | <mo>+</mo> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mo>×</mo> |
| | | <mn>174</mn> |
| | | <mo>−</mo> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>106</mn> |
| | | <mo>×</mo> |
| | | <mn>166</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>166</mn> |
| | | <mo>×</mo> |
| | | <mn>174</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>544</mn> |
| | | </mrow> |
| | | <mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>98</mn> |
| | | <mo>×</mo> |
| | | <mn>174</mn> |
| | | <mo>−</mo> |
| | | <mn>106</mn> |
| | | <mo>×</mo> |
| | | <mn>166</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>166</mn> |
| | | <mo>×</mo> |
| | | <mn>174</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>544</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>166</mn> |
| | | <mo>×</mo> |
| | | <mn>174</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | </math>,所以<math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | <mo>×</mo> |
| | | </mfrac> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mn>106</mn> |
| | | <mn>174</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | </math>,所以<math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mn>106</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 又因为<math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo>≈</mo> |
| | | <mn>0.590</mn> |
| | | <mn>4</mn> |
| | | </math>,<math display="0"> |
| | | <mfrac> |
| | | <mn>106</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | <mo>≈</mo> |
| | | <mn>0.690</mn> |
| | | <mn>2</mn> |
| | | </math>,所以立起脚尖后,该芭蕾舞演员的下半身长与全身长的比值更接近0.618. |
| | | </p> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 又因为<math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo>≈</mo> |
| | | <mn>0.590</mn> |
| | | <mn>4</mn> |
| | | </math>,<math display="0"> |
| | | <mfrac> |
| | | <mn>106</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | <mo>≈</mo> |
| | | <mn>0.690</mn> |
| | | <mn>2</mn> |
| | | </math>,所以立起脚尖后,该芭蕾舞演员的下半身长与全身长的比值更接近0.618. |
| | | </p> |
| | | </div> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | |
| | | </math>. |
| | | </p> |
| | | </div> |
| | | |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 已知<i>b</i>><i>a</i>>0,<i>c</i>>0,比较<math display="0"> |
| | | <p class="p-btn"> |
| | | <span class="zt-ls"><b>例2</b></span> |
| | | <span calss="t1">已知b>a>0,c>0,比较</span> |
| | | <math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | </math>的大小. |
| | | <span class="btn-box" @click="isShowAnswer5 = !isShowAnswer5"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 作差可得<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <div v-if="isShowAnswer5"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 作差可得<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mi>a</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | <mo>−</mo> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>b</mi> |
| | | <mo>−</mo> |
| | | <mi>a</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 因为<i>b</i>><i>a</i>>0,所以<i>b</i>-<i>a</i>>0.又因为<i>c</i>>0,所以<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | <mo>−</mo> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 因为<i>b</i>><i>a</i>>0,所以<i>b</i>-<i>a</i>>0.又因为<i>c</i>>0,所以<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>b</mi> |
| | | <mo>−</mo> |
| | | <mi>a</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | </math>, |
| | | </p> |
| | | <p> |
| | | 即<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | </math>, |
| | | </p> |
| | | <p> |
| | | 即<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | </math>,所以<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | </mfrac> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | </math>,所以<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>></mo> |
| | | <mfrac> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>></mo> |
| | | <mfrac> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | </div> |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"> |
| | |
| | | <p>第二单元 不等式</p> |
| | | </li> |
| | | <li> |
| | | <p><span>039</span></p> |
| | | <p><span>039-041</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | |
| | | 区间也是一个集合,它是实数集的一个子集.但并非所有的数集都能用区间表示.例如,集合{1,3,4,5,7,8,11,12}、自然数集<b>N</b>、整数集<b>Z</b>就不能用区间表示. |
| | | </p> |
| | | </div> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 把下列集合用区间表示出来,并指出区间的类型. |
| | | <p class="p-btn"> |
| | | <span class="zt-ls"><b>例1</b></span> |
| | | <span class="t1">把下列集合用区间表示出来,并指出区间的类型.</span> |
| | | <span class="btn-box" @click="isShowAnswer6 = !isShowAnswer6"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p>(1) {<i>x</i>|-3≤<i>x</i>≤1};(2) {<i>x</i>|-1<<i>x</i><2};</p> |
| | | <p> |
| | |
| | | </math>; |
| | | </p> |
| | | <p>(5) {<i>x</i>|<i>x</i>≥2};(6) {<i>x</i>|<i>x</i><1}.</p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) [-3,1],是闭区间; |
| | | <div v-if="isShowAnswer6"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) [-3,1],是闭区间; |
| | | </p> |
| | | <p>(2)(-1,2),是开区间;</p> |
| | | <p> |
| | | (3) |
| | | <math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">[</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mn>4</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,是左闭右开区间; |
| | | </p> |
| | | <p> |
| | | (4) |
| | | <math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mn>6</mn> |
| | | <mo>,</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">]</mo> |
| | | </mrow> |
| | | </math>,是左开右闭区间; |
| | | </p> |
| | | <p>(5) [2,+∞),是左闭右开区间;</p> |
| | | <p>(6)(-∞,1),是开区间.</p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | <span class="zt-ls"><b>例2</b></span> |
| | | <span class="t1">用区间表示不等式3<i>x</i><9<i>x</i>+4的解集,并在数轴上表示出来.</span> |
| | | <span class="btn-box" @click="isShowAnswer7 = !isShowAnswer7"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p>(2)(-1,2),是开区间;</p> |
| | | <p> |
| | | (3) |
| | | <math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">[</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mn>4</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,是左闭右开区间; |
| | | <div v-if="isShowAnswer7"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 解不等式3<i>x</i><9<i>x</i>+4,得 |
| | | </p> |
| | | <math display="block"> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p> |
| | | 所以不等式的解集用区间表示为<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mo>+</mo> |
| | | <mi mathvariant="normal">∞</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,表示在数轴上如图2-1所示. |
| | | </p> |
| | | <p class="center"><img class="img-f" alt="" src="../../assets/images/0050-7.jpg" /></p> |
| | | <p class="img">图2-1</p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | <span class="zt-ls"><b>例3</b></span> |
| | | <span class="t1">设<b>R</b>为全集,集合A={x|-5<x<6},B={x|x≥3或x≤-3},用区间表示A∩B.</span> |
| | | <span class="btn-box" @click="isShowAnswer8 = !isShowAnswer8"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | (4) |
| | | <math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mn>6</mn> |
| | | <mo>,</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">]</mo> |
| | | </mrow> |
| | | </math>,是左开右闭区间; |
| | | </p> |
| | | <p>(5) [2,+∞),是左闭右开区间;</p> |
| | | <p>(6)(-∞,1),是开区间.</p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 用区间表示不等式3<i>x</i><9<i>x</i>+4的解集,并在数轴上表示出来. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 解不等式3<i>x</i><9<i>x</i>+4,得 |
| | | </p> |
| | | <math display="block"> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p> |
| | | 所以不等式的解集用区间表示为<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mo>+</mo> |
| | | <mi mathvariant="normal">∞</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,表示在数轴上如图2-1所示. |
| | | </p> |
| | | <p class="center"><img class="img-f" alt="" src="../../assets/images/0050-7.jpg" /></p> |
| | | <p class="img">图2-1</p> |
| | | <p> |
| | | <span |
| | | class="zt-ls"><b>例3</b></span> 设<b>R</b>为全集,集合<i>A</i>={<i>x</i>|-5<<i>x</i><6},<i>B</i>={<i>x</i>|<i>x</i>≥3或<i>x</i>≤-3},用区间表示<i>A</i>∩<i>B</i>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 在数轴上将集合<i>A</i>,<i>B</i>表示出来,如图2-2所示. |
| | | </p> |
| | | <p class="center"><img class="img-d" alt="" src="../../assets/images/0050-8.jpg" /></p> |
| | | <p class="img">图2-2</p> |
| | | <p> |
| | | <i>A</i>∩<i>B</i>={<i>x</i>|-5<<i>x</i><6}∩{<i>x</i>|<i>x</i>≥3或<i>x</i>≤-3} |
| | | </p> |
| | | <p>={<i>x</i>|-5<<i>x</i>≤-3}∪{<i>x</i>|3≤<i>x</i><6}</p> |
| | | <p>=(-5,-3]∪[3,6).</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 040 --> |
| | | <div class="page-box" page="47"> |
| | | <div v-if="showPageList.indexOf(47) > -1"> |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>040-041</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <div v-if="isShowAnswer8"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 在数轴上将集合<i>A</i>,<i>B</i>表示出来,如图2-2所示. |
| | | </p> |
| | | <p class="center"><img class="img-d" alt="" src="../../assets/images/0050-8.jpg" /></p> |
| | | <p class="img">图2-2</p> |
| | | <p> |
| | | <i>A</i>∩<i>B</i>={<i>x</i>|-5<<i>x</i><6}∩{<i>x</i>|<i>x</i>≥3或<i>x</i>≤-3} |
| | | </p> |
| | | <p>={<i>x</i>|-5<<i>x</i>≤-3}∪{<i>x</i>|3≤<i>x</i><6}</p> |
| | | <p>=(-5,-3]∪[3,6).</p> |
| | | </div> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | |
| | | </div> |
| | | <h3 id="c015">习题2.2<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[47] ? questionData[47][2] : []" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | <examinations :cardList="questionData[47] ? questionData[47][2] : []" :hideCollect="true" sourceType="json" |
| | | inputBc="#d3edfa" v-if="questionData"></examinations> |
| | | </div> |
| | | <h2 id="b009"> |
| | | 2.3 一元二次不等式<span class="fontsz1">>>>>>>>></span> |
| | |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 040 --> |
| | | <div class="page-box hidePage" page="47"> |
| | | </div> |
| | | <!-- 041 --> |
| | | <div class="page-box hidePage" page="48"> |
| | |
| | | </math>,与<i>y</i>轴的交点坐标为(0,<i>c</i>). |
| | | </p> |
| | | </div> |
| | | <p><b>例</b> 已知二次函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>-3,</p> |
| | | <p>(1) 画出该函数图像;</p> |
| | | <p> |
| | | <p class="p-btn"> |
| | | <b>例</b> |
| | | <span>已知二次函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>-3,</span> |
| | | <span class="btn-box" @click="openDialog(thinkOne)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
| | | d="M3771.2-14311.889a2.356,2.356,0,0,1-1.727-.626c-.027-.054-.053-.1-.079-.148l0-.007c-.123-.224-.2-.371-.076-.629a.869.869,0,0,1,.784-.471.205.205,0,0,1,.158.079.205.205,0,0,0,.158.079.187.187,0,0,0,.038.1.143.143,0,0,0,.117.05h.158a.573.573,0,0,0,.471.158,2.2,2.2,0,0,0,.916-.3l.023-.011a.572.572,0,0,1,.471-.158.575.575,0,0,1,.626.626.526.526,0,0,1,.036.409.664.664,0,0,1-.349.375A3.582,3.582,0,0,1,3771.2-14311.889Zm-1.885-1.723h-.155a.718.718,0,0,1-.784-.63.38.38,0,0,1-.021-.3.976.976,0,0,1,.492-.485l4.86-1.252a1.047,1.047,0,0,1,.784.626c.151.3-.128.61-.471.784l-4.705,1.256Zm-.155-1.885H3769a.716.716,0,0,1-.784-.626c-.149-.3.129-.611.471-.784l4.234-1.1v-.158l-.021.007a7.808,7.808,0,0,1-1.861.31,5.3,5.3,0,0,1-3.137-.942,5.789,5.789,0,0,1-2.666-4.076,6.421,6.421,0,0,1,1.256-5.018,7.038,7.038,0,0,1,2.194-1.568,7.848,7.848,0,0,1,2.666-.472,6.43,6.43,0,0,1,2.979.784,4.958,4.958,0,0,1,2.2,2.194,5.522,5.522,0,0,1,.313,5.177,13.113,13.113,0,0,1-1.256,1.882l-.313.313a2.156,2.156,0,0,0-.78,1.244l0,.012a1.731,1.731,0,0,1-1.727,1.723l-.313.158-3.292.939Zm1.256-6.271v1.256h1.41v-1.256Zm.784-4.234c.718,0,1.1.271,1.1.784a.925.925,0,0,1-.316.783l-.468.156a2.235,2.235,0,0,0-.63.471l-.012.024a2.2,2.2,0,0,0-.3.918v.155h1.1v-.155a1.2,1.2,0,0,1,.313-.629.543.543,0,0,0,.315-.153c.007,0,.315,0,.315-.16a1.226,1.226,0,0,0,.626-.626,2.277,2.277,0,0,0,.313-1.1,1.409,1.409,0,0,0-.626-1.252,2.337,2.337,0,0,0-1.569-.471,2.258,2.258,0,0,0-2.507,2.353l1.252.154A1.121,1.121,0,0,1,3771.2-14326Zm-6.51,9.645a.769.769,0,0,1-.549-.237.772.772,0,0,1-.235-.549.772.772,0,0,1,.235-.548l.939-.939a.781.781,0,0,1,.55-.234.772.772,0,0,1,.547.234.772.772,0,0,1,.238.549.772.772,0,0,1-.238.549l-.939.938A.769.769,0,0,1,3764.686-14316.356Zm13.174-.157a.774.774,0,0,1-.549-.234l-.943-.942a.678.678,0,0,1-.233-.47.678.678,0,0,1,.233-.47.774.774,0,0,1,.549-.234.774.774,0,0,1,.549.234l.942.939a.427.427,0,0,1,.228.324.74.74,0,0,1-.228.618A.774.774,0,0,1,3777.859-14316.514Zm2.9-6.351h-1.414c-.469-.158-.784-.474-.784-.784a.743.743,0,0,1,.784-.784h1.414a.743.743,0,0,1,.784.784A.743.743,0,0,1,3780.761-14322.864Zm-17.566-.158h-1.41c-.469-.157-.784-.473-.784-.784a.743.743,0,0,1,.784-.784h1.41a.743.743,0,0,1,.784.784A.743.743,0,0,1,3763.195-14323.022Zm13.861-5.723a.759.759,0,0,1-.529-.237.776.776,0,0,1-.235-.549.772.772,0,0,1,.235-.549l.939-.938a.44.44,0,0,1,.413-.238.759.759,0,0,1,.529.238.772.772,0,0,1,.235.549.772.772,0,0,1-.235.548l-.942.939A.435.435,0,0,1,3777.055-14328.745Zm-11.429,0a.776.776,0,0,1-.55-.237l-.939-1.1a.678.678,0,0,1-.235-.469.678.678,0,0,1,.235-.47.772.772,0,0,1,.549-.238.772.772,0,0,1,.549.238l.939,1.1a.675.675,0,0,1,.238.47.675.675,0,0,1-.238.47A.767.767,0,0,1,3765.626-14328.745Zm5.724-2.273a.743.743,0,0,1-.784-.785v-1.413c.157-.469.473-.784.784-.784a.743.743,0,0,1,.784.784v1.413A.743.743,0,0,1,3771.35-14331.019Z" |
| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="p-btn"> |
| | | (1) 画出该函数图像; |
| | | <span class="btn-box" @click="isShowAnswer9 = !isShowAnswer9"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer9"> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0055-1.jpg" /></p> |
| | | <p class="img">图2-3</p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 因为<i>a</i>=1>0,所以函数图像为开口向上的抛物线. |
| | | </p> |
| | | <p> |
| | | 因为<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(-2)<sup>2</sup>-4×1×(-3)=16>0, |
| | | </p> |
| | | <p> |
| | | 所以一元二次方程<i>x</i><sup>2</sup>-2<i>x</i>-3=0有两个不相等的实数解. |
| | | </p> |
| | | <p>解方程,得<i>x</i><sub>1</sub>=-1,<i>x</i><sub>2</sub>=3.</p> |
| | | <p>所以抛物线与<i>x</i>轴的交点坐标为(-1,0),(3,0).</p> |
| | | <p> |
| | | 抛物线的顶点坐标为<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>a</mi> |
| | | <mi>c</mi> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,即(1,-4). |
| | | </p> |
| | | <p> |
| | | 抛物线的对称轴方程为<math display="0"> |
| | | <mi>x</mi> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>,即<i>x</i>=1.抛物线与<i>y</i>轴的交点坐标为(0,<i>c</i>),即(0,-3).根据函数的对称性,可以再取一些点,如(2,-3). |
| | | </p> |
| | | <p> |
| | | 根据以上信息,就可以画出函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>-3的图像(如图2-3所示). |
| | | </p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | (2) |
| | | 指出该函数图像上纵坐标分别为<i>y</i>=0,<i>y</i>>0,<i>y</i><0的所有点; |
| | | 指出该函数图像上纵坐标分别为y=0,y>0,y<0的所有点; |
| | | <span class="btn-box" @click="isShowAnswer10 = !isShowAnswer10"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <p v-if="isShowAnswer10"> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | (2) |
| | | 观察图像可知,满足<i>y</i>=0的点是抛物线与<i>x</i>轴的交点;满足<i>y</i>>0的点是抛物线在<i>x</i>轴上方的所有点;满足<i>y</i><0的点是抛物线在<i>x</i>轴下方的所有点. |
| | | </p> |
| | | <p class="p-btn"> |
| | | (3) |
| | | 根据函数图像写出<i>y</i>=0,<i>y</i>>0,<i>y</i><0时所对应的<i>x</i>的值或取值范围. |
| | | 根据函数图像写出y=0,y>0,y<0时所对应的x的值或取值范围. |
| | | <span class="btn-box" @click="isShowAnswer11 = !isShowAnswer11"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="block"> |
| | | <span |
| | | class="zt-ls2"><b>分析</b></span> ①根据<i>x</i><sup>2</sup>的系数判断函数图像(抛物线)的开口方向;②用判别式判定出一元二次方程<i>x</i><sup>2</sup>-2<i>x</i>-3=0的解的情况,从而确定二次函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>-3的图像与<i>x</i>轴的交点个数和交点坐标;③计算二次函数图像的顶点坐标、与<i>y</i>轴的交点坐标;④求出二次函数图像的对称轴方程,并利用函数图像的对称性再找出一些点;⑤最后根据上述信息画出函数图像. |
| | | </p> |
| | | <p class="block"> |
| | | 画出图像后,<i>y</i>=0,<i>y</i>>0,<i>y</i><0分别对应函数图像与<i>x</i>轴相交、函数图像在<i>x</i>轴上方、函数图像在<i>x</i>轴下方三种情形,根据图像完成(2)(3) |
| | | 两个问题. |
| | | </p> |
| | | <div v-if="isShowAnswer11"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | (3) |
| | | 观察图像可知,当<i>y</i>=0时,对应抛物线与<i>x</i>轴的两个交点,此时<i>x</i>有两个取值,<i>x</i><sub>1</sub>=-1,<i>x</i><sub>2</sub>=3; |
| | | </p> |
| | | <p> |
| | | 当<i>y</i>>0时,对应抛物线在<i>x</i>轴上方的所有点,此时<i>x</i>的取值范围是<i>x</i><-1或<i>x</i>>3; |
| | | </p> |
| | | <p> |
| | | 当<i>y</i><0时,对应抛物线在<i>x</i>轴下方的所有点,此时<i>x</i>的取值范围是-1<<i>x</i><3. |
| | | </p> |
| | | </div> |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" class="iframe-box"></iframe> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0055-1.jpg" /></p> |
| | | <p class="img">图2-3</p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 因为<i>a</i>=1>0,所以函数图像为开口向上的抛物线. |
| | | </p> |
| | | <p> |
| | | 因为<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(-2)<sup>2</sup>-4×1×(-3)=16>0, |
| | | </p> |
| | | <p> |
| | | 所以一元二次方程<i>x</i><sup>2</sup>-2<i>x</i>-3=0有两个不相等的实数解. |
| | | </p> |
| | | <p>解方程,得<i>x</i><sub>1</sub>=-1,<i>x</i><sub>2</sub>=3.</p> |
| | | <p>所以抛物线与<i>x</i>轴的交点坐标为(-1,0),(3,0).</p> |
| | | <p> |
| | | 抛物线的顶点坐标为<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>a</mi> |
| | | <mi>c</mi> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,即(1,-4). |
| | | </p> |
| | | <p> |
| | | 抛物线的对称轴方程为<math display="0"> |
| | | <mi>x</mi> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>,即<i>x</i>=1.抛物线与<i>y</i>轴的交点坐标为(0,<i>c</i>),即(0,-3).根据函数的对称性,可以再取一些点,如(2,-3). |
| | | </p> |
| | | <p> |
| | | 根据以上信息,就可以画出函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>-3的图像(如图2-3所示). |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 观察图像可知,满足<i>y</i>=0的点是抛物线与<i>x</i>轴的交点;满足<i>y</i>>0的点是抛物线在<i>x</i>轴上方的所有点;满足<i>y</i><0的点是抛物线在<i>x</i>轴下方的所有点. |
| | | </p> |
| | | <p> |
| | | (3) |
| | | 观察图像可知,当<i>y</i>=0时,对应抛物线与<i>x</i>轴的两个交点,此时<i>x</i>有两个取值,<i>x</i><sub>1</sub>=-1,<i>x</i><sub>2</sub>=3; |
| | | </p> |
| | | <p> |
| | | 当<i>y</i>>0时,对应抛物线在<i>x</i>轴上方的所有点,此时<i>x</i>的取值范围是<i>x</i><-1或<i>x</i>>3; |
| | | </p> |
| | | <p> |
| | | 当<i>y</i><0时,对应抛物线在<i>x</i>轴下方的所有点,此时<i>x</i>的取值范围是-1<<i>x</i><3. |
| | | </p> |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"> |
| | | <img class="img-gn2" alt="" src="../../assets/images/hzjl.jpg" /> |
| | | </p> |
| | | </div> |
| | | <examinations :cardList="questionData[51] ? questionData[51][1] : []" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | <examinations :cardList="questionData[51] ? questionData[51][1] : []" :hideCollect="true" sourceType="json" |
| | | inputBc="#d3edfa" v-if="questionData"></examinations> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /></p> |
| | | <div class="bj"> |
| | | <p>已知下列二次函数:</p> |
| | | <p>①<i>y</i>=<i>x</i><sup>2</sup>-3<i>x</i>-4, ②<i>y</i>=<i>x</i><sup>2</sup>+<i>x</i>+2, ③<i>y</i>=<i>x</i><sup>2</sup>-6<i>x</i>+9.</p> |
| | | <p>①<i>y</i>=<i>x</i><sup>2</sup>-3<i>x</i>-4, ②<i>y</i>=<i>x</i><sup>2</sup>+<i>x</i>+2, |
| | | ③<i>y</i>=<i>x</i><sup>2</sup>-6<i>x</i>+9.</p> |
| | | <p>(1) 分别画出它们的函数图像;</p> |
| | | <paint |
| | | :page="51" |
| | | :imgUrl="this.config.activeBook.resourceUrl + '/images/a6fe3d63.png'" |
| | | /> |
| | | <paint :page="51" :imgUrl="this.config.activeBook.resourceUrl + '/images/a6fe3d63.png'" /> |
| | | <p> |
| | | (2) 根据函数图像写出<i>y</i>=0,<i>y</i>>0,<i>y</i><0时所对应的<i>x</i>的值或取值范围. |
| | | <span class="btn-box" @click="isShowAnswer = !isShowAnswer"> |
| | |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <el-input type="textarea" placeholder="请输入内容" rows="6" class="question-textarea" ></el-input> |
| | | <el-input type="textarea" placeholder="请输入内容" rows="6" class="question-textarea"></el-input> |
| | | <ul class="table-answer-box" v-if="isShowAnswer"> |
| | | <li>答案:</li> |
| | | <li> |
| | | <math display="block"> <mrow> <mo>①</mo> </mrow> <mi>y</mi> <mo>=</mo> <msup> <mi>x</mi> <mrow> <mn>2</mn> </mrow> </msup> <mo>−</mo> <mn>3</mn> <mi>x</mi> <mo>−</mo> <mn>4</mn> <mo>=</mo> <mo stretchy="false">(</mo> <mi>x</mi> <mo>+</mo> <mn>1</mn> <mo stretchy="false">)</mo> <mo stretchy="false">(</mo> <mi>x</mi> <mo>−</mo> <mn>4</mn> <mo stretchy="false">)</mo></math> |
| | | <math display="block"> <mo>当</mo> <mi>y</mi> <mo>=</mo> <mn>0</mn> <mo>时,</mo> <msub> <mi>x</mi> <mrow> <mn>1</mn> </mrow> </msub> <mo>=</mo> <mo>−</mo> <mn>1</mn> <mo>或</mo> <msub> <mi>x</mi> <mrow> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mn>4</mn> <mo>,</mo></math> |
| | | <math display="block"> <mo>当</mo> <mi>y</mi> <mo>></mo> <mn>0</mn> <mo>时,</mo> <mi>x</mi> <mo><</mo> <mo>−</mo> <mn>1</mn> <mo>或</mo> <mi>x</mi> <mo>></mo> <mn>4</mn> <mo>,</mo></math> |
| | | <math display="block"> <mo>当</mo> <mi>y</mi> <mo><</mo> <mn>0</mn> <mo>时,</mo> <mo>−</mo> <mn>1</mn> <mo><</mo> <mi>x</mi> <mo><</mo> <mn>4</mn> <mo>;</mo></math> |
| | | <math display="block"> <mo>因此当</mo> <mi>y</mi> <mo>=</mo> <mn>0</mn> <mo>时,所对应的点为</mo> <mo stretchy="false">(</mo> <mo>−</mo> <mn>1</mn> <mo>,</mo> <mn>0</mn> <mo stretchy="false">)</mo> <mo>,</mo> <mo stretchy="false">(</mo> <mn>4</mn> <mo>,</mo> <mn>0</mn> <mo stretchy="false">)</mo> <mo>;</mo> <mo>当</mo> <mi>y</mi> <mo>></mo> <mn>0</mn> <mo>时,所对应的点为</mo> </math> |
| | | <math display="block"> <mo stretchy="false">(</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo>,</mo> <mi>y</mi> <mo stretchy="false">)</mo> <mo>,其中,</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo><</mo> <mo>−</mo> <mn>1</mn> <mo>或</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo>></mo> <mn>4</mn> <mo>;</mo> </math> |
| | | <math display="block"> <mo>当</mo> <mi>y</mi> <mo><</mo> <mn>0</mn> <mo>时,所对应的点为</mo> <mo stretchy="false">(</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo>,</mo> <mi>y</mi> <mo stretchy="false">)</mo> <mo>,其中</mo> <mo>−</mo> <mn>1</mn> <mo><</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo><</mo> <mn>4</mn> <mo>;</mo></math> |
| | | <math display="block"> <mrow> <mo>②</mo> </mrow> <mi>y</mi> <mo>=</mo> <msup> <mi>x</mi> <mrow> <mn>2</mn> </mrow> </msup> <mo>+</mo> <mi>x</mi> <mo>+</mo> <mn>2</mn> <mo>=</mo> <mo stretchy="false">(</mo> <mi>x</mi> <mo>+</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <msup> <mo stretchy="false">)</mo> <mrow> <mn>2</mn> </mrow> </msup> <mo>+</mo> <mfrac> <mn>7</mn> <mn>4</mn> </mfrac> <mo>></mo> <mn>0</mn> <mo>;</mo></math> |
| | | <math display="block"> <mo>当</mo> <mi>y</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mi>y</mi> <mo><</mo> <mn>0</mn> <mo>时,没有对应的点;当</mo> <mi>y</mi> <mo>></mo> <mn>0</mn> <mo>时,所对应的点为</mo> <mo stretchy="false">(</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo>,</mo> <mi>y</mi> <mo stretchy="false">)</mo> </math> |
| | | <math> <mo>,其中</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo>∈</mo> <mi>R</mi> <mo>.</mo></math> |
| | | <math display="block"> <mrow> <mo>③</mo> </mrow> <mi>y</mi> <mo>=</mo> <msup> <mi>x</mi> <mrow> <mn>2</mn> </mrow> </msup> <mo>−</mo> <mn>6</mn> <mi>x</mi> <mo>+</mo> <mn>9</mn> <mo>=</mo> <mo stretchy="false">(</mo> <mi>x</mi> <mo>−</mo> <mn>3</mn> <msup> <mo stretchy="false">)</mo> <mrow> <mn>2</mn> </mrow> </msup> <mo>.</mo></math> |
| | | <math display="block"> <mo>当</mo> <mi>y</mi> <mo>=</mo> <mn>0</mn> <mo>时</mo> <mo>,</mo> <mo>所对应的点为</mo> <mo stretchy="false">(</mo> <mn>3</mn> <mo>,</mo> <mn>0</mn> <mo stretchy="false">)</mo> <mo>;当</mo> <mi>y</mi> <mo>></mo> <mn>0</mn> <mo>时,所对应的点为</mo> <mo stretchy="false">(</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo>,</mo> <mi>y</mi> <mo stretchy="false">)</mo> </math> |
| | | <math display="block"> <mo>,其中</mo> <msub> <mi>x</mi> <mrow> <mn>0</mn> </mrow> </msub> <mo>≠</mo> <mn>3</mn> <mo>;当</mo> <mi>y</mi> <mo><</mo> <mn>0</mn> <mo>时,没有对应的点</mo> <mo>.</mo></math> |
| | | <math display="block"> |
| | | <mrow> |
| | | <mo>①</mo> |
| | | </mrow> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>4</mn> |
| | | <mo>=</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>4</mn> |
| | | <mo stretchy="false">)</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo>当</mo> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mn>0</mn> |
| | | <mo>时,</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo>或</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>=</mo> |
| | | <mn>4</mn> |
| | | <mo>,</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo>当</mo> |
| | | <mi>y</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>时,</mo> |
| | | <mi>x</mi> |
| | | <mo><</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo>或</mo> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>4</mn> |
| | | <mo>,</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo>当</mo> |
| | | <mi>y</mi> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | <mo>时,</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo><</mo> |
| | | <mn>4</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo>因此当</mo> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mn>0</mn> |
| | | <mo>时,所对应的点为</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo>,</mo> |
| | | <mn>0</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>,</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mn>4</mn> |
| | | <mo>,</mo> |
| | | <mn>0</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>;</mo> |
| | | <mo>当</mo> |
| | | <mi>y</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>时,所对应的点为</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo stretchy="false">(</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>,</mo> |
| | | <mi>y</mi> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>,其中,</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo><</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo>或</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>></mo> |
| | | <mn>4</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo>当</mo> |
| | | <mi>y</mi> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | <mo>时,所对应的点为</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>,</mo> |
| | | <mi>y</mi> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>,其中</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo><</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo><</mo> |
| | | <mn>4</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mrow> |
| | | <mo>②</mo> |
| | | </mrow> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>2</mn> |
| | | <mo>=</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <msup> |
| | | <mo stretchy="false">)</mo> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>7</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo>当</mo> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mi>y</mi> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | <mo>时,没有对应的点;当</mo> |
| | | <mi>y</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>时,所对应的点为</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>,</mo> |
| | | <mi>y</mi> |
| | | <mo stretchy="false">)</mo> |
| | | </math> |
| | | <math> |
| | | <mo>,其中</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>∈</mo> |
| | | <mi>R</mi> |
| | | <mo>.</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mrow> |
| | | <mo>③</mo> |
| | | </mrow> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>−</mo> |
| | | <mn>6</mn> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>9</mn> |
| | | <mo>=</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <msup> |
| | | <mo stretchy="false">)</mo> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>.</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo>当</mo> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mn>0</mn> |
| | | <mo>时</mo> |
| | | <mo>,</mo> |
| | | <mo>所对应的点为</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mn>3</mn> |
| | | <mo>,</mo> |
| | | <mn>0</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>;当</mo> |
| | | <mi>y</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>时,所对应的点为</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>,</mo> |
| | | <mi>y</mi> |
| | | <mo stretchy="false">)</mo> |
| | | </math> |
| | | <math display="block"> |
| | | <mo>,其中</mo> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>≠</mo> |
| | | <mn>3</mn> |
| | | <mo>;当</mo> |
| | | <mi>y</mi> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | <mo>时,没有对应的点</mo> |
| | | <mo>.</mo> |
| | | </math> |
| | | </li> |
| | | </ul> |
| | | </div> |
| | |
| | | 上面的情形表明,二次函数图像的开口方向及其与<i>x</i>轴的交点坐标,可以确定其对应的一元二次不等式的解集. |
| | | </p> |
| | | <p><b>例</b> 利用二次函数的图像解下列一元二次不等式.</p> |
| | | <p> |
| | | (1) -<i>x</i><sup>2</sup>+3<i>x</i>+4<0;(2) <i>x</i><sup>2</sup>-2<i>x</i>+3>0. |
| | | <p class="p-btn" > |
| | | <span>(1) -<i>x</i><sup>2</sup>+3<i>x</i>+4<0;</span> |
| | | <span class="btn-box" @click="isShowAnswer12 = !isShowAnswer12"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0057-1.jpg" /></p> |
| | | <p class="img">图2-5</p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) |
| | | Δ=<i>b</i><sup>2</sup>-4<i>ac</i>=3<sup>2</sup>-4×(-1)×4=25>0,所以函数<i>y</i>=-<i>x</i><sup>2</sup>+3<i>x</i>+4的图像与<i>x</i>轴有两个交点.解方程-<i>x</i><sup>2</sup>+3<i>x</i>+4=0可得,<i>x</i>1=-1,<i>x</i>2=4. |
| | | <div v-if="isShowAnswer12" > |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0057-1.jpg" /></p> |
| | | <p class="img">图2-5</p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) |
| | | Δ=<i>b</i><sup>2</sup>-4<i>ac</i>=3<sup>2</sup>-4×(-1)×4=25>0,所以函数<i>y</i>=-<i>x</i><sup>2</sup>+3<i>x</i>+4的图像与<i>x</i>轴有两个交点.解方程-<i>x</i><sup>2</sup>+3<i>x</i>+4=0可得,<i>x</i>1=-1,<i>x</i>2=4. |
| | | </p> |
| | | <p> |
| | | 函数<i>y</i>=-<i>x</i><sup>2</sup>+3<i>x</i>+4的图像是开口向下的抛物线,与<i>x</i>轴的交点坐标是(-1,0),(4,0),函数<i>y</i>=-<i>x</i><sup>2</sup>+3<i>x</i>+4的图像如图2-5所示. |
| | | </p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(2) <i>x</i><sup>2</sup>-2<i>x</i>+3>0.</span> |
| | | <span class="btn-box" @click="isShowAnswer13 = !isShowAnswer13"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | 函数<i>y</i>=-<i>x</i><sup>2</sup>+3<i>x</i>+4的图像是开口向下的抛物线,与<i>x</i>轴的交点坐标是(-1,0),(4,0),函数<i>y</i>=-<i>x</i><sup>2</sup>+3<i>x</i>+4的图像如图2-5所示. |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0057-2.jpg" /></p> |
| | | <p class="img">图2-6</p> |
| | | <p> |
| | | 观察图像可得,不等式-<i>x</i><sup>2</sup>+3<i>x</i>+4<0的解集是(-∞, |
| | | -1)∪(4, +∞). |
| | | </p> |
| | | <p> |
| | | (2) |
| | | <i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(-2)<sup>2</sup>-4×1×3=-8<0,所以函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>+3的图像与<i>x</i>轴无交点. |
| | | </p> |
| | | <p> |
| | | 函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>+3的图像是开口向上的抛物线,与<i>x</i>轴无交点,其简图如图2-6所示. |
| | | </p> |
| | | <p> |
| | | 观察图像可得,不等式<i>x</i><sup>2</sup>-2<i>x</i>+3>0的解集为<b>R</b>. |
| | | </p> |
| | | <div v-if="isShowAnswer13" > |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0057-2.jpg" /></p> |
| | | <p class="img">图2-6</p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 观察图像可得,不等式-<i>x</i><sup>2</sup>+3<i>x</i>+4<0的解集是(-∞, |
| | | -1)∪(4, +∞). |
| | | </p> |
| | | <p> |
| | | (2) |
| | | <i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(-2)<sup>2</sup>-4×1×3=-8<0,所以函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>+3的图像与<i>x</i>轴无交点. |
| | | </p> |
| | | <p> |
| | | 函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>+3的图像是开口向上的抛物线,与<i>x</i>轴无交点,其简图如图2-6所示. |
| | | </p> |
| | | <p> |
| | | 观察图像可得,不等式<i>x</i><sup>2</sup>-2<i>x</i>+3>0的解集为<b>R</b>. |
| | | </p> |
| | | </div> |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" class="iframe-box"></iframe> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | |
| | | <img class="img-gn2" alt="" src="../../assets/images/hzjl.jpg" /> |
| | | </p> |
| | | </div> |
| | | <examinations :cardList="questionData[54] ? questionData[54][1] : []" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | <examinations :cardList="questionData[54] ? questionData[54][1] : []" :hideCollect="true" sourceType="json" |
| | | v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /></p> |
| | |
| | | </p> |
| | | <p>第三步:观察简图,写出不等式的解集.</p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[54] ? questionData[54][2] : []" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | <examinations :cardList="questionData[54] ? questionData[54][2] : []" :hideCollect="true" sourceType="json" |
| | | inputBc="#d3edfa" v-if="questionData"></examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 解下列不等式. |
| | | </p> |
| | | <p> |
| | | (1)(<i>x</i>+3)(<i>x</i>+1)<0;(2)(6-<i>x</i>)(<i>x</i>+4)≤0. |
| | | <p class="p-btn" > |
| | | <span>(1)(<i>x</i>+3)(<i>x</i>+1)<0;</span> |
| | | <span class="btn-box" @click="isShowAnswer14 = !isShowAnswer14"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1)(<i>x</i>+3)(<i>x</i>+1)<0,即[<i>x</i>-(-3)][<i>x</i>-(-1)]<0. |
| | | <div v-if="isShowAnswer14" > |
| | | <p > |
| | | <span class="zt-ls"><b>解</b></span>(1)(<i>x</i>+3)(<i>x</i>+1)<0,即[<i>x</i>-(-3)][<i>x</i>-(-1)]<0. |
| | | </p> |
| | | <p >所以不等式的解集为(-3,-1).</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(2)(6-<i>x</i>)(<i>x</i>+4)≤0.</span> |
| | | <span class="btn-box" @click="isShowAnswer15 = !isShowAnswer15"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p>所以不等式的解集为(-3,-1).</p> |
| | | <p> |
| | | <div v-if="isShowAnswer15" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | (2) |
| | | 由(6-<i>x</i>)(<i>x</i>+4)≤0得(<i>x</i>-6)(<i>x</i>+4)≥0,即 |
| | | 由(6-<i>x</i>)(<i>x</i>+4)≤0得(<i>x</i>-6)(<i>x</i>+4)≥0,即 |
| | | </p> |
| | | <p class="center">(<i>x</i>-6)[<i>x</i>-(-4)]≥0.</p> |
| | | <p>所以不等式的解集为(-∞,-4]∪[6,+∞).</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例2</b></span> 解下列不等式. |
| | | </span> |
| | | <span class="btn-box" @click="openDialog(thinkTwo)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
| | | d="M3771.2-14311.889a2.356,2.356,0,0,1-1.727-.626c-.027-.054-.053-.1-.079-.148l0-.007c-.123-.224-.2-.371-.076-.629a.869.869,0,0,1,.784-.471.205.205,0,0,1,.158.079.205.205,0,0,0,.158.079.187.187,0,0,0,.038.1.143.143,0,0,0,.117.05h.158a.573.573,0,0,0,.471.158,2.2,2.2,0,0,0,.916-.3l.023-.011a.572.572,0,0,1,.471-.158.575.575,0,0,1,.626.626.526.526,0,0,1,.036.409.664.664,0,0,1-.349.375A3.582,3.582,0,0,1,3771.2-14311.889Zm-1.885-1.723h-.155a.718.718,0,0,1-.784-.63.38.38,0,0,1-.021-.3.976.976,0,0,1,.492-.485l4.86-1.252a1.047,1.047,0,0,1,.784.626c.151.3-.128.61-.471.784l-4.705,1.256Zm-.155-1.885H3769a.716.716,0,0,1-.784-.626c-.149-.3.129-.611.471-.784l4.234-1.1v-.158l-.021.007a7.808,7.808,0,0,1-1.861.31,5.3,5.3,0,0,1-3.137-.942,5.789,5.789,0,0,1-2.666-4.076,6.421,6.421,0,0,1,1.256-5.018,7.038,7.038,0,0,1,2.194-1.568,7.848,7.848,0,0,1,2.666-.472,6.43,6.43,0,0,1,2.979.784,4.958,4.958,0,0,1,2.2,2.194,5.522,5.522,0,0,1,.313,5.177,13.113,13.113,0,0,1-1.256,1.882l-.313.313a2.156,2.156,0,0,0-.78,1.244l0,.012a1.731,1.731,0,0,1-1.727,1.723l-.313.158-3.292.939Zm1.256-6.271v1.256h1.41v-1.256Zm.784-4.234c.718,0,1.1.271,1.1.784a.925.925,0,0,1-.316.783l-.468.156a2.235,2.235,0,0,0-.63.471l-.012.024a2.2,2.2,0,0,0-.3.918v.155h1.1v-.155a1.2,1.2,0,0,1,.313-.629.543.543,0,0,0,.315-.153c.007,0,.315,0,.315-.16a1.226,1.226,0,0,0,.626-.626,2.277,2.277,0,0,0,.313-1.1,1.409,1.409,0,0,0-.626-1.252,2.337,2.337,0,0,0-1.569-.471,2.258,2.258,0,0,0-2.507,2.353l1.252.154A1.121,1.121,0,0,1,3771.2-14326Zm-6.51,9.645a.769.769,0,0,1-.549-.237.772.772,0,0,1-.235-.549.772.772,0,0,1,.235-.548l.939-.939a.781.781,0,0,1,.55-.234.772.772,0,0,1,.547.234.772.772,0,0,1,.238.549.772.772,0,0,1-.238.549l-.939.938A.769.769,0,0,1,3764.686-14316.356Zm13.174-.157a.774.774,0,0,1-.549-.234l-.943-.942a.678.678,0,0,1-.233-.47.678.678,0,0,1,.233-.47.774.774,0,0,1,.549-.234.774.774,0,0,1,.549.234l.942.939a.427.427,0,0,1,.228.324.74.74,0,0,1-.228.618A.774.774,0,0,1,3777.859-14316.514Zm2.9-6.351h-1.414c-.469-.158-.784-.474-.784-.784a.743.743,0,0,1,.784-.784h1.414a.743.743,0,0,1,.784.784A.743.743,0,0,1,3780.761-14322.864Zm-17.566-.158h-1.41c-.469-.157-.784-.473-.784-.784a.743.743,0,0,1,.784-.784h1.41a.743.743,0,0,1,.784.784A.743.743,0,0,1,3763.195-14323.022Zm13.861-5.723a.759.759,0,0,1-.529-.237.776.776,0,0,1-.235-.549.772.772,0,0,1,.235-.549l.939-.938a.44.44,0,0,1,.413-.238.759.759,0,0,1,.529.238.772.772,0,0,1,.235.549.772.772,0,0,1-.235.548l-.942.939A.435.435,0,0,1,3777.055-14328.745Zm-11.429,0a.776.776,0,0,1-.55-.237l-.939-1.1a.678.678,0,0,1-.235-.469.678.678,0,0,1,.235-.47.772.772,0,0,1,.549-.238.772.772,0,0,1,.549.238l.939,1.1a.675.675,0,0,1,.238.47.675.675,0,0,1-.238.47A.767.767,0,0,1,3765.626-14328.745Zm5.724-2.273a.743.743,0,0,1-.784-.785v-1.413c.157-.469.473-.784.784-.784a.743.743,0,0,1,.784.784v1.413A.743.743,0,0,1,3771.35-14331.019Z" |
| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="center">(<i>x</i>-6)[<i>x</i>-(-4)]≥0.</p> |
| | | <p>所以不等式的解集为(-∞,-4]∪[6,+∞).</p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 解下列不等式. |
| | | <p class="p-btn" > |
| | | <span>(1)(<i>x</i>+1)<sup>2</sup>≥4;</span> |
| | | <span class="btn-box" @click="isShowAnswer16 = !isShowAnswer16"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | (1)(<i>x</i>+1)<sup>2</sup>≥4;(2)(2<i>x</i>-3)<sup>2</sup><9. |
| | | <div v-if="isShowAnswer16" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) |
| | | 由(<i>x</i>+1)<sup>2</sup>≥4得(<i>x</i>+1)<sup>2</sup>-2<sup>2</sup>≥0, |
| | | </p> |
| | | <p>从而 [(<i>x</i>+1)+2][(<i>x</i>+1)-2]≥0,</p> |
| | | <p>化简得(<i>x</i>+3)(<i>x</i>-1)≥0,</p> |
| | | <p>即 [<i>x</i>-(-3)](<i>x</i>-1)≥0,</p> |
| | | <p>所以不等式的解集为(-∞,-3]∪[1,+∞).</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(2)(2<i>x</i>-3)<sup>2</sup><9.</span> |
| | | <span class="btn-box" @click="isShowAnswer17 = !isShowAnswer17"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="block"> |
| | | <span |
| | | class="zt-ls2"><b>分析</b></span> 由(<i>x</i>+1)<sup>2</sup>≥4得<i>x</i><sup>2</sup>+2<i>x</i>+1≥4,即<i>x</i><sup>2</sup>+2<i>x</i>-3≥0,从而可以利用二次函数<i>y</i>=<i>x</i><sup>2</sup>+2<i>x</i>-3的图像进行求解;注意到4=2<sup>2</sup>,也可以考虑将(<i>x</i>+1)<sup>2</sup>≥4整理为(<i>x</i>+1)<sup>2</sup>-4≥0,并使用平方差公式,即(<i>x</i>+1)<sup>2</sup>-2<sup>2</sup>≥0,得到(<i>x</i>+3)(<i>x</i>-1)≥0,此时可以借助上面的结论直接求解.下面我们将使用后一种方法进行求解. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) |
| | | 由(<i>x</i>+1)<sup>2</sup>≥4得(<i>x</i>+1)<sup>2</sup>-2<sup>2</sup>≥0, |
| | | </p> |
| | | <p>从而 [(<i>x</i>+1)+2][(<i>x</i>+1)-2]≥0,</p> |
| | | <p>化简得(<i>x</i>+3)(<i>x</i>-1)≥0,</p> |
| | | <p>即 [<i>x</i>-(-3)](<i>x</i>-1)≥0,</p> |
| | | <p>所以不等式的解集为(-∞,-3]∪[1,+∞).</p> |
| | | <p> |
| | | (2) |
| | | 由(2<i>x</i>-3)<sup>2</sup><9得(2<i>x</i>-3)<sup>2</sup>-3<sup>2</sup><0, |
| | | </p> |
| | | <p>从而 [(2<i>x</i>-3)+3][(2<i>x</i>-3)-3]<0,</p> |
| | | <p>化简得 2<i>x</i>(2<i>x</i>-6)<0,</p> |
| | | <p>即 <i>x</i>(<i>x</i>-3)<0,</p> |
| | | <p>即(<i>x</i>-0)(<i>x</i>-3)<0,</p> |
| | | <p>所以不等式的解集为(0,3).</p> |
| | | <div v-if="isShowAnswer17" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | (2) |
| | | 由(2<i>x</i>-3)<sup>2</sup><9得(2<i>x</i>-3)<sup>2</sup>-3<sup>2</sup><0, |
| | | </p> |
| | | <p>从而 [(2<i>x</i>-3)+3][(2<i>x</i>-3)-3]<0,</p> |
| | | <p>化简得 2<i>x</i>(2<i>x</i>-6)<0,</p> |
| | | <p>即 <i>x</i>(<i>x</i>-3)<0,</p> |
| | | <p>即(<i>x</i>-0)(<i>x</i>-3)<0,</p> |
| | | <p>所以不等式的解集为(0,3).</p> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /></p> |
| | | <div class="bj"> |
| | | <p>解下列一元二次不等式.</p> |
| | |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p><b>例</b> 解不等式|2<i>x</i>|<5.</p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 由|2<i>x</i>|<5得-5<2<i>x</i><5, |
| | | <p class="p-btn" > |
| | | <span> |
| | | <b>例</b> 解不等式|2<i>x</i>|<5. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer18 = !isShowAnswer18"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | 即 <math display="0"> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 所以不等式的解集是<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <div v-if="isShowAnswer18" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 由|2<i>x</i>|<5得-5<2<i>x</i><5, |
| | | </p> |
| | | <p> |
| | | 即 <math display="0"> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>. |
| | | </p> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 所以不等式的解集是<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>. |
| | | </p> |
| | | </div> |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"> |
| | | <img class="img-gn2" alt="" src="../../assets/images/hzjl.jpg" /> |
| | | </p> |
| | | </div> |
| | | <examinations :cardList="questionData[60] ? questionData[60][1] : []" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | <examinations :cardList="questionData[60] ? questionData[60][1] : []" :hideCollect="true" sourceType="json" |
| | | inputBc="#d3edfa" v-if="questionData"></examinations> |
| | | </div> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[60] ? questionData[60][2] : []" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | <examinations :cardList="questionData[60] ? questionData[60][2] : []" :hideCollect="true" sourceType="json" |
| | | inputBc="#d3edfa" v-if="questionData"></examinations> |
| | | </div> |
| | | <h3 id="c021"> |
| | | 2.4.2 |
| | |
| | | <p> |
| | | 求解此类不等式时,可以将<i>ax</i>+<i>b</i>看作一个整体,再利用含绝对值不等式的基本解法,去掉绝对值,然后进行求解. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 解不等式|2<i>x</i>-1|<5. |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例1</b></span> 解不等式|2<i>x</i>-1|<5. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer19 = !isShowAnswer19"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 由|2<i>x</i>-1|<5得-5<2<i>x</i>-1<5, |
| | | <div v-if="isShowAnswer19" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 由|2<i>x</i>-1|<5得-5<2<i>x</i>-1<5, |
| | | </p> |
| | | <p>即 -4<2<i>x</i><6,</p> |
| | | <p> -2<<i>x</i><3.</p> |
| | | <p>所以不等式的解集是(-2,3).</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例2</b></span> 解不等式|1-2<i>x</i>|<3. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer20 = !isShowAnswer20"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p>即 -4<2<i>x</i><6,</p> |
| | | <p> -2<<i>x</i><3.</p> |
| | | <p>所以不等式的解集是(-2,3).</p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 解不等式|1-2<i>x</i>|<3. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 因为|1-2<i>x</i>|=|2<i>x</i>-1|, |
| | | </p> |
| | | <p>所以由|1-2<i>x</i>|<3得|2<i>x</i>-1|<3.</p> |
| | | <div v-if="isShowAnswer20" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 因为|1-2<i>x</i>|=|2<i>x</i>-1|, |
| | | </p> |
| | | <p>所以由|1-2<i>x</i>|<3得|2<i>x</i>-1|<3.</p> |
| | | <p>由|2<i>x</i>-1|<3得-3<2<i>x</i>-1<3,</p> |
| | | <p>即 -2<2<i>x</i><4,</p> |
| | | <p> -1<<i>x</i><2.</p> |
| | | <p>所以不等式的解集是(-1,2).</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p>由|2<i>x</i>-1|<3得-3<2<i>x</i>-1<3,</p> |
| | | <p>即 -2<2<i>x</i><4,</p> |
| | | <p> -1<<i>x</i><2.</p> |
| | | <p>所以不等式的解集是(-1,2).</p> |
| | | <p> |
| | | <span class="zt-ls"><b>例3</b></span> 解不等式|<i>x</i>+3|≥2. |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例3</b></span> 解不等式|<i>x</i>+3|≥2. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer21 = !isShowAnswer21"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 由|<i>x</i>+3|≥2得<i>x</i>+3≤-2或<i>x</i>+3≥2, |
| | | <div v-if="isShowAnswer21" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 由|<i>x</i>+3|≥2得<i>x</i>+3≤-2或<i>x</i>+3≥2, |
| | | </p> |
| | | <p>即 <i>x</i>≤-5或<i>x</i>≥-1.</p> |
| | | <p>所以不等式的解集是(-∞,-5]∪[-1,+∞).</p> |
| | | <p> |
| | | 现在我们回到本节开始的问题,解不等式|<i>x</i>-100|≤3得97≤<i>x</i>≤103,解不等式|<i>x</i>-100|>3得<i>x</i>>103或<i>x</i><97.如果产权登记面积在97 |
| | | m<sup>2</sup>和103 m<sup>2</sup>之间(包含97 m<sup>2</sup>和103 |
| | | m<sup>2</sup>) |
| | | 时,李先生按照产权登记面积结算房款;如果产权登记面积小于97 |
| | | m<sup>2</sup>或大于103 m<sup>2</sup>时,李先生有权退房. |
| | | </p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例4</b></span> 解不等式|3<i>x</i>-(<i>x</i>-2)|≤2. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer22 = !isShowAnswer22"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p>即 <i>x</i>≤-5或<i>x</i>≥-1.</p> |
| | | <p>所以不等式的解集是(-∞,-5]∪[-1,+∞).</p> |
| | | <p> |
| | | 现在我们回到本节开始的问题,解不等式|<i>x</i>-100|≤3得97≤<i>x</i>≤103,解不等式|<i>x</i>-100|>3得<i>x</i>>103或<i>x</i><97.如果产权登记面积在97 |
| | | m<sup>2</sup>和103 m<sup>2</sup>之间(包含97 m<sup>2</sup>和103 |
| | | m<sup>2</sup>) |
| | | 时,李先生按照产权登记面积结算房款;如果产权登记面积小于97 |
| | | m<sup>2</sup>或大于103 m<sup>2</sup>时,李先生有权退房. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例4</b></span> 解不等式|3<i>x</i>-(<i>x</i>-2)|≤2. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 由|3<i>x</i>-(<i>x</i>-2)|≤2得|3<i>x</i>-<i>x</i>+2|≤2, |
| | | </p> |
| | | <p>即 |2<i>x</i>+2|≤2,</p> |
| | | <p>从而 -2≤2<i>x</i>+2≤2,</p> |
| | | <p> -4≤2<i>x</i>≤0,</p> |
| | | <p> -2≤<i>x</i>≤0.</p> |
| | | <p>所以不等式的解集是[-2,0].</p> |
| | | <div v-if="isShowAnswer22"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 由|3<i>x</i>-(<i>x</i>-2)|≤2得|3<i>x</i>-<i>x</i>+2|≤2, |
| | | </p> |
| | | <p>即 |2<i>x</i>+2|≤2,</p> |
| | | <p>从而 -2≤2<i>x</i>+2≤2,</p> |
| | | <p> -4≤2<i>x</i>≤0,</p> |
| | | <p> -2≤<i>x</i>≤0.</p> |
| | | <p>所以不等式的解集是[-2,0].</p> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /></p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[61]" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | |
| | | </h3> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0066-11.jpg" /></p> |
| | | <p class="img">图2-12</p> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 用篱笆在墙边围一块矩形小花坛,其中一边靠墙(如图2-12所示),篱笆总长为8m.若小花坛的面积不小于6 |
| | | m<sup>2</sup>,则小花坛垂直于墙的一边的长度范围是多少? |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例1</b></span> 用篱笆在墙边围一块矩形小花坛,其中一边靠墙(如图2-12所示),篱笆总长为8m.若小花坛的面积不小于6 |
| | | m<sup>2</sup>,则小花坛垂直于墙的一边的长度范围是多少? |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer23 = !isShowAnswer23"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <p v-if="isShowAnswer23" > |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 设小花坛垂直于墙的一边的长度为<i>x</i>(m),则与墙平行的一边的长度为(8-2<i>x</i>)m.考虑到实际情况,有<i>x</i>>0,并且8-2<i>x</i>>0,所以<i>x</i>满足0<<i>x</i><4. |
| | | </p> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p>设小花坛的面积为<i>S</i>(m<sup>2</sup>),则</p> |
| | | <p class="center"><i>S</i>=<i>x</i>(8-2<i>x</i>),</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0067-1.jpg" /></p> |
| | | <p class="img">图2-13</p> |
| | | <p>整理得 <i>S</i>=-2<i>x</i><sup>2</sup>+8<i>x</i>.</p> |
| | | <p> |
| | | 由题意得 <i>S</i>=-2<i>x</i><sup>2</sup>+8<i>x</i>≥6,即<i>x</i><sup>2</sup>-4<i>x</i>+3≤0. |
| | | </p> |
| | | <p> |
| | | 画出二次函数<i>y</i>=<i>x</i><sup>2</sup>-4<i>x</i>+3的简图(如图2-13所示). |
| | | </p> |
| | | <p>由图像得不等式的解为{<i>x</i>|1≤<i>x</i>≤3}.</p> |
| | | <p>结合0<<i>x</i><4,得</p> |
| | | <p class="center"> |
| | | {<i>x</i>|0<<i>x</i><4}∩{<i>x</i>|1≤<i>x</i>≤3}={<i>x</i>|1≤<i>x</i>≤3}. |
| | | </p> |
| | | <p>所以小花坛垂直于墙的一边的长度在1m至3m之间(含1m和3m).</p> |
| | | <p> |
| | | <span |
| | | <div v-if="isShowAnswer23"> |
| | | <p>设小花坛的面积为<i>S</i>(m<sup>2</sup>),则</p> |
| | | <p class="center"><i>S</i>=<i>x</i>(8-2<i>x</i>),</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0067-1.jpg" /></p> |
| | | <p class="img">图2-13</p> |
| | | <p>整理得 <i>S</i>=-2<i>x</i><sup>2</sup>+8<i>x</i>.</p> |
| | | <p> |
| | | 由题意得 <i>S</i>=-2<i>x</i><sup>2</sup>+8<i>x</i>≥6,即<i>x</i><sup>2</sup>-4<i>x</i>+3≤0. |
| | | </p> |
| | | <p> |
| | | 画出二次函数<i>y</i>=<i>x</i><sup>2</sup>-4<i>x</i>+3的简图(如图2-13所示). |
| | | </p> |
| | | <p>由图像得不等式的解为{<i>x</i>|1≤<i>x</i>≤3}.</p> |
| | | <p>结合0<<i>x</i><4,得</p> |
| | | <p class="center"> |
| | | {<i>x</i>|0<<i>x</i><4}∩{<i>x</i>|1≤<i>x</i>≤3}={<i>x</i>|1≤<i>x</i>≤3}. |
| | | </p> |
| | | <p>所以小花坛垂直于墙的一边的长度在1m至3m之间(含1m和3m).</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span |
| | | class="zt-ls"><b>例2</b></span> 某网店销售一种电动玩具,成本为10元/个.平时按单价20元销售,日平均销售量为100个.为进一步提升业绩,该网店决定在“双11”期间举办降价促销活动.根据以往的统计,如果该电动玩具的单价每降低0.5元,日平均销售量就会大约增加10个.为了使促销活动期间日平均利润不低于平时,应如何确定降价的范围? |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer24 = !isShowAnswer24"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | <span class="btn-box" @click="openDialog(thinkThree)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
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| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="block"> |
| | | <span |
| | | class="zt-ls2"><b>分析</b></span> 利润=(销售单价-成本单价)×销售量.降价过程中,单价降低能够使销售量变大,但也使销售单价与成本单价的差减小,所以降价的范围应保证利润不低于促销前. |
| | | </p> |
| | | <div class="bk"> |
| | | <div class="bk mt-60" > |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/tbts.jpg" /> |
| | |
| | | 由例1和例2可知,在解决与一元二次不等式有关的实际问题时,不仅要解一元二次不等式,而且要考虑实际背景对未知数的限制.在例1中,实际背景对未知数的限制是0<<i>x</i><4;在例2中,实际背景对未知数的限制是0<<i>x</i><10. |
| | | </p> |
| | | </div> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 假设降价<i>x</i>元.考虑到实际情况,价格的降幅应小于10元,即保证销售价高于成本价,所以要求<i>x</i>>0并且<i>x</i><10,即0<<i>x</i><10. |
| | | </p> |
| | | <p>平时的日平均利润为(20-10)×100=1 000(元).</p> |
| | | <p> |
| | | 降价<i>x</i>元后,销售单价为(20-<i>x</i>)元,单个玩具的利润为(20-<i>x</i>)-10=(10-<i>x</i>)元,日平均销售量为<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>100</mn> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>10</mn> |
| | | <mn>0.5</mn> |
| | | </mfrac> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>个.因此,降价<i>x</i>元后的日平均利润为(10-<i>x</i>)(100+20<i>x</i>)元. |
| | | </p> |
| | | <p>由题意得(10-<i>x</i>)(100+20<i>x</i>)≥1 000.</p> |
| | | <p>化简得<i>x</i><sup>2</sup>-5<i>x</i>≤0,即<i>x</i>(<i>x</i>-5)≤0.</p> |
| | | <p>所以不等式的解集为 {<i>x</i>|0≤<i>x</i>≤5}.</p> |
| | | <p> |
| | | 由于0<<i>x</i><10,所以<i>x</i>的范围是{<i>x</i>|0<<i>x</i><10}∩{<i>x</i>|0≤<i>x</i>≤5},即{<i>x</i>|0<<i>x</i>≤5}.所以降价的范围应在0至5元之间(含5元,不含0元),即单价定在15元至20元之间(含15元,不含20元),便能满足要求. |
| | | </p> |
| | | <div v-if="isShowAnswer24"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 假设降价<i>x</i>元.考虑到实际情况,价格的降幅应小于10元,即保证销售价高于成本价,所以要求<i>x</i>>0并且<i>x</i><10,即0<<i>x</i><10. |
| | | </p> |
| | | <p>平时的日平均利润为(20-10)×100=1 000(元).</p> |
| | | <p> |
| | | 降价<i>x</i>元后,销售单价为(20-<i>x</i>)元,单个玩具的利润为(20-<i>x</i>)-10=(10-<i>x</i>)元,日平均销售量为<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>100</mn> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>10</mn> |
| | | <mn>0.5</mn> |
| | | </mfrac> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>个.因此,降价<i>x</i>元后的日平均利润为(10-<i>x</i>)(100+20<i>x</i>)元. |
| | | </p> |
| | | <p>由题意得(10-<i>x</i>)(100+20<i>x</i>)≥1 000.</p> |
| | | <p>化简得<i>x</i><sup>2</sup>-5<i>x</i>≤0,即<i>x</i>(<i>x</i>-5)≤0.</p> |
| | | <p>所以不等式的解集为 {<i>x</i>|0≤<i>x</i>≤5}.</p> |
| | | <p> |
| | | 由于0<<i>x</i><10,所以<i>x</i>的范围是{<i>x</i>|0<<i>x</i><10}∩{<i>x</i>|0≤<i>x</i>≤5},即{<i>x</i>|0<<i>x</i>≤5}.所以降价的范围应在0至5元之间(含5元,不含0元),即单价定在15元至20元之间(含15元,不含20元),便能满足要求. |
| | | </p> |
| | | </div> |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"> |
| | |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0068-1.jpg" /></p> |
| | | <p class="img">第2题图</p> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /></p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[64]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | |
| | | <h3 id="c024"> |
| | | 2.5.2 不等式与复杂实际问题<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p> |
| | | <span |
| | | class="zt-ls"><b>例1</b></span> 我国交通法规对小型汽车驾驶员的年龄限制如下:最低年龄18周岁,最高年龄70周岁.已有研究表明,小型汽车驾驶员对红绿灯变化的反应时间<i>y</i>(ms) |
| | | 与驾驶员年龄<i>x</i>(周岁) |
| | | 的关系为<i>y</i>=0.005<i>x</i><sup>2</sup>-0.2<i>x</i>+22,其中18≤<i>x</i>≤70.问:反应时间超过24.5ms的驾驶员所处的年龄范围是多少? |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span |
| | | class="zt-ls"><b>例1</b></span> 我国交通法规对小型汽车驾驶员的年龄限制如下:最低年龄18周岁,最高年龄70周岁.已有研究表明,小型汽车驾驶员对红绿灯变化的反应时间<i>y</i>(ms) |
| | | 与驾驶员年龄<i>x</i>(周岁) |
| | | 的关系为<i>y</i>=0.005<i>x</i><sup>2</sup>-0.2<i>x</i>+22,其中18≤<i>x</i>≤70.问:反应时间超过24.5ms的驾驶员所处的年龄范围是多少? |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer25 = !isShowAnswer25"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 由题意得,<i>y</i>=0.005<i>x</i><sup>2</sup>-0.2<i>x</i>+22>24.5,即 |
| | | </p> |
| | | <p> 0.005<i>x</i><sup>2</sup>-0.2<i>x</i>-2.5>0.</p> |
| | | <p>化简得 <i>x</i><sup>2</sup>-40<i>x</i>-500>0.</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0068-2.jpg" /></p> |
| | | <p class="img">图2-14</p> |
| | | <p> |
| | | 考查二次函数<i>y</i>=<i>x</i><sup>2</sup>-40<i>x</i>-500,<i>a</i>=1>0,<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(-40)<sup>2</sup>-4×1×(-500)=3 |
| | | 600>0,所以二次函数<i>y</i>=<i>x</i><sup>2</sup>-40<i>x</i>-500的图像开口向上,并且与<i>x</i>轴有两个交点.其简图如图2-14所示. |
| | | </p> |
| | | <p> |
| | | 由图像可知,不等式<i>x</i><sup>2</sup>-40<i>x</i>-500>0的解集为(-∞,-10)∪(50,+∞),这也是不等式0.005<i>x</i><sup>2</sup>-0.2<i>x</i>-2.5>0的解集. |
| | | </p> |
| | | <p> |
| | | 考虑到18≤<i>x</i>≤70,所以<i>x</i>的范围是(50,70],即反应时间超过24.5 |
| | | <i>ms</i> |
| | | 的驾驶员所处的年龄范围在50岁至70岁之间(不包含50岁,包含70岁). |
| | | </p> |
| | | <div v-if="isShowAnswer25" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 由题意得,<i>y</i>=0.005<i>x</i><sup>2</sup>-0.2<i>x</i>+22>24.5,即 |
| | | </p> |
| | | <p> 0.005<i>x</i><sup>2</sup>-0.2<i>x</i>-2.5>0.</p> |
| | | <p>化简得 <i>x</i><sup>2</sup>-40<i>x</i>-500>0.</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0068-2.jpg" /></p> |
| | | <p class="img">图2-14</p> |
| | | <p> |
| | | 考查二次函数<i>y</i>=<i>x</i><sup>2</sup>-40<i>x</i>-500,<i>a</i>=1>0,<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(-40)<sup>2</sup>-4×1×(-500)=3 |
| | | 600>0,所以二次函数<i>y</i>=<i>x</i><sup>2</sup>-40<i>x</i>-500的图像开口向上,并且与<i>x</i>轴有两个交点.其简图如图2-14所示. |
| | | </p> |
| | | <p> |
| | | 由图像可知,不等式<i>x</i><sup>2</sup>-40<i>x</i>-500>0的解集为(-∞,-10)∪(50,+∞),这也是不等式0.005<i>x</i><sup>2</sup>-0.2<i>x</i>-2.5>0的解集. |
| | | </p> |
| | | <p> |
| | | 考虑到18≤<i>x</i>≤70,所以<i>x</i>的范围是(50,70],即反应时间超过24.5 |
| | | <i>ms</i> |
| | | 的驾驶员所处的年龄范围在50岁至70岁之间(不包含50岁,包含70岁). |
| | | </p> |
| | | </div> |
| | | |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 身体质量指数(Body Mass |
| | | Index,BMI)是衡量人体胖瘦程度的一个常用标准,计算公式为<math display="0"> |
| | |
| | | 000m跑、女生800m跑),坐位体前屈等项目的成绩总和.身体素质指标为正数说明身体素质较好.上述研究发现,身体素质指标(<i>y</i>)与BMI(<i>x</i>) |
| | | 之间的关系如表2-7所示. |
| | | </p> |
| | | <p>问:身体素质较好的男生和女生,其BMI的范围分别是多少?</p> |
| | | <p class="p-btn" > |
| | | 问:身体素质较好的男生和女生,其BMI的范围分别是多少? |
| | | <span class="btn-box" @click="isShowAnswer26 = !isShowAnswer26"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="img">表2-7</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0069-1.jpg" /></p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 先考虑男生的情况.由题意得,<i>y</i>=-0.05<i>x</i><sup>2</sup>+2<i>x</i>-19.2>0,即 |
| | | </p> |
| | | <p class="center">0.05<i>x</i><sup>2</sup>-2<i>x</i>+19.2<0.</p> |
| | | <p>化简得 <i>x</i><sup>2</sup>-40<i>x</i>+384<0.</p> |
| | | <p> |
| | | 考查二次函数<i>y</i>=<i>x</i><sup>2</sup>-40<i>x</i>+384,<i>a</i>=1>0,<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=40<sup>2</sup>-4×1×384=64>0,所以二次函数<i>y</i>=<i>x</i><sup>2</sup>-40<i>x</i>+384的图像开口向上,与<i>x</i>轴有两个交点. |
| | | </p> |
| | | <p> |
| | | 所以不等式<i>x</i><sup>2</sup>-40<i>x</i>+384<0的解集为(16,24),这也是不等式-0.05<i>x</i><sup>2</sup>+2<i>x</i>-19.2>0的解集. |
| | | </p> |
| | | <p> |
| | | 再考虑女生的情况.由题意得,<i>y</i>=-0.01<i>x</i><sup>2</sup>+0.39<i>x</i>-3.68>0,即 |
| | | </p> |
| | | <p class="center">0.01<i>x</i><sup>2</sup>-0.39<i>x</i>+3.68<0.</p> |
| | | <p>化简得 <i>x</i><sup>2</sup>-39<i>x</i>+368<0.</p> |
| | | <p> |
| | | 考查二次函数<i>y</i>=<i>x</i><sup>2</sup>-39<i>x</i>+368,<i>a</i>=1>0,<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(-39)<sup>2</sup>-4×1×368=49>0,所以二次函数<i>y</i>=<i>x</i><sup>2</sup>-39<i>x</i>+368的图像开口向上,与<i>x</i>轴有两个交点. |
| | | </p> |
| | | <p> |
| | | 所以不等式<i>x</i><sup>2</sup>-39<i>x</i>+368<0的解集为(16,23),这也是不等式-0.01<i>x</i><sup>2</sup>+0.39<i>x</i>-3.68>0的解集. |
| | | </p> |
| | | <p> |
| | | 因此,身体素质较好的男生BMI 的范围是(16,24),身体素质较好的女生BMI |
| | | 的范围是(16,23). |
| | | </p> |
| | | <div v-if="isShowAnswer26" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 先考虑男生的情况.由题意得,<i>y</i>=-0.05<i>x</i><sup>2</sup>+2<i>x</i>-19.2>0,即 |
| | | </p> |
| | | <p class="center">0.05<i>x</i><sup>2</sup>-2<i>x</i>+19.2<0.</p> |
| | | <p>化简得 <i>x</i><sup>2</sup>-40<i>x</i>+384<0.</p> |
| | | <p> |
| | | 考查二次函数<i>y</i>=<i>x</i><sup>2</sup>-40<i>x</i>+384,<i>a</i>=1>0,<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=40<sup>2</sup>-4×1×384=64>0,所以二次函数<i>y</i>=<i>x</i><sup>2</sup>-40<i>x</i>+384的图像开口向上,与<i>x</i>轴有两个交点. |
| | | </p> |
| | | <p> |
| | | 所以不等式<i>x</i><sup>2</sup>-40<i>x</i>+384<0的解集为(16,24),这也是不等式-0.05<i>x</i><sup>2</sup>+2<i>x</i>-19.2>0的解集. |
| | | </p> |
| | | <p> |
| | | 再考虑女生的情况.由题意得,<i>y</i>=-0.01<i>x</i><sup>2</sup>+0.39<i>x</i>-3.68>0,即 |
| | | </p> |
| | | <p class="center">0.01<i>x</i><sup>2</sup>-0.39<i>x</i>+3.68<0.</p> |
| | | <p>化简得 <i>x</i><sup>2</sup>-39<i>x</i>+368<0.</p> |
| | | <p> |
| | | 考查二次函数<i>y</i>=<i>x</i><sup>2</sup>-39<i>x</i>+368,<i>a</i>=1>0,<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(-39)<sup>2</sup>-4×1×368=49>0,所以二次函数<i>y</i>=<i>x</i><sup>2</sup>-39<i>x</i>+368的图像开口向上,与<i>x</i>轴有两个交点. |
| | | </p> |
| | | <p> |
| | | 所以不等式<i>x</i><sup>2</sup>-39<i>x</i>+368<0的解集为(16,23),这也是不等式-0.01<i>x</i><sup>2</sup>+0.39<i>x</i>-3.68>0的解集. |
| | | </p> |
| | | <p> |
| | | 因此,身体素质较好的男生BMI 的范围是(16,24),身体素质较好的女生BMI |
| | | 的范围是(16,23). |
| | | </p> |
| | | </div> |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"> |
| | | <img class="img-gn2" alt="" src="../../assets/images/hzjl.jpg" /> |
| | | </p> |
| | | </div> |
| | | <examinations :cardList="questionData[65]" :hideCollect="true" sourceType="json" |
| | | v-if="questionData" ></examinations> |
| | | <examinations :cardList="questionData[65]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[66] ? questionData[66][1] : []" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | <examinations :cardList="questionData[66] ? questionData[66][1] : []" :hideCollect="true" sourceType="json" |
| | | inputBc="#d3edfa" v-if="questionData"></examinations> |
| | | </div> |
| | | <h3 id="c025">习题2.5<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[66] ? questionData[66][2] : []" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | <examinations :cardList="questionData[66] ? questionData[66][2] : []" :hideCollect="true" sourceType="json" |
| | | v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | |
| | | <!-- 066 --> |
| | | <div class="page-box hidePage" page="73"> |
| | | </div> |
| | | <!-- 解题思路弹窗 --> |
| | | <el-dialog :visible.sync="thinkingDialog" width="40%" :append-to-body="true" :show-close="false" |
| | | @close="closeDialog" class="thinkDialog"> |
| | | <div slot="title" class="think-header" |
| | | style="padding: 0; text-align: center; color: #333;display:flex;justify-content: center;"> |
| | | <span style=""> 分析 </span> |
| | | <svg style="position: absolute; right:10px;cursor: pointer;" @click="thinkingDialog = false" t="1718596022986" |
| | | class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="4252" width="20" |
| | | height="20" xmlns:xlink="http://www.w3.org/1999/xlink"> |
| | | <path |
| | | d="M176.661601 817.172881C168.472798 825.644055 168.701706 839.149636 177.172881 847.338438 185.644056 855.527241 199.149636 855.298332 207.338438 846.827157L826.005105 206.827157C834.193907 198.355983 833.964998 184.850403 825.493824 176.661601 817.02265 168.472798 803.517069 168.701706 795.328267 177.172881L176.661601 817.172881Z" |
| | | fill="#979797" p-id="4253"></path> |
| | | <path |
| | | d="M795.328267 846.827157C803.517069 855.298332 817.02265 855.527241 825.493824 847.338438 833.964998 839.149636 834.193907 825.644055 826.005105 817.172881L207.338438 177.172881C199.149636 168.701706 185.644056 168.472798 177.172881 176.661601 168.701706 184.850403 168.472798 198.355983 176.661601 206.827157L795.328267 846.827157Z" |
| | | fill="#979797" p-id="4254"></path> |
| | | </svg> |
| | | </div> |
| | | <ul> |
| | | <li v-for="(item, index) in thinkData" :key="index"> |
| | | <div v-if="index <= showIndex" style="display: flex"> |
| | | <span style="position: relative"> |
| | | <span style="position: absolute; top: 16px; left: 13px; color: #fff">{{ index + 1 }}</span> |
| | | <img src="../../assets/images/icon/blue-group.png" alt="" style="margin-right: 10px" |
| | | v-if="index < thinkOne.length - 1" /> |
| | | <img src="../../assets/images/icon/blue.png" alt="" v-if="index == thinkOne.length - 1" |
| | | style="margin-right: 10px" /> |
| | | </span> |
| | | <p class="txt-p" v-html="item"></p> |
| | | </div> |
| | | </li> |
| | | </ul> |
| | | <div @click="changeNext" style=" |
| | | display: flex; |
| | | flex-direction: column; |
| | | align-items: center; |
| | | justify-content: center; |
| | | "> |
| | | <img src="../../assets/images/icon/mouse.png" alt="" v-if="showIndex < thinkData.length - 1" /> |
| | | <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" t="1710234570135" |
| | | class="icon" viewBox="0 0 1024 1024" version="1.1" p-id="5067" width="15" height="15"> |
| | | <path |
| | | d="M2.257993 493.371555 415.470783 906.584344 512 1003.113561 608.529217 906.584344 1021.742007 493.371555 925.212789 396.842337 512 810.055127 98.787211 396.842337Z" |
| | | fill="#1296db" p-id="5068" /> |
| | | <path |
| | | d="M2.257993 117.980154 415.470783 531.192944 512 627.722161 608.529217 531.192944 1021.742007 117.980154 925.212789 21.450937 512 434.663727 98.787211 21.450937Z" |
| | | fill="#1296db" p-id="5069" /> |
| | | </svg> |
| | | </div> |
| | | </el-dialog> |
| | | </div> |
| | | </template> |
| | | |
| | | <script> |
| | | const handleShow = (num) => { |
| | | const obj = {} |
| | | for (let index = 0; index < num; index++) { |
| | | obj['isShowAnswer' + index] = false |
| | | } |
| | | return obj |
| | | } |
| | | const showObj = handleShow(30) |
| | | import paint from '@/components/paint/index.vue' |
| | | import examinations from '@/components/examinations/index.vue' |
| | | export default { |
| | |
| | | type: Object, |
| | | }, |
| | | }, |
| | | components: { examinations,paint }, |
| | | components: { examinations, paint }, |
| | | data() { |
| | | return { |
| | | isShowAnswer:false |
| | | collectImg: require('../../assets/images/icon/heart.png'), |
| | | collectCheck: require('../../assets/images/icon/heart-check.png'), |
| | | thinkingDialog: false, |
| | | showIndex: 0, |
| | | thinkData: [], |
| | | thinkOne: [ |
| | | '①根据<i>x</i><sup>2</sup>的系数判断函数图像(抛物线)的开口方向;', |
| | | '②用判别式判定出一元二次方程<i>x</i><sup>2</sup>-2<i>x</i>-3=0的解的情况,从而确定二次函数<i>y</i>=<i>x</i><sup>2</sup>-2<i>x</i>-3的图像与<i>x</i>轴的交点个数和交点坐标;', |
| | | '③计算二次函数图像的顶点坐标、与<i>y</i>轴的交点坐标;', |
| | | '④求出二次函数图像的对称轴方程,并利用函数图像的对称性再找出一些点;⑤最后根据上述信息画出函数图像.', |
| | | '画出图像后,<i>y</i>=0,<i>y</i>>0,<i>y</i><0分别对应函数图像与<i>x</i>轴相交、函数图像在<i>x</i>轴上方、函数图像在<i>x</i>轴下方三种情形,根据图像完成(2)(3)两个问题.' |
| | | ], |
| | | thinkTwo:[ |
| | | '由(<i>x</i>+1)<sup>2</sup>≥4得<i>x</i><sup>2</sup>+2<i>x</i>+1≥4,即<i>x</i><sup>2</sup>+2<i>x</i>-3≥0,从而可以利用二次函数<i>y</i>=<i>x</i><sup>2</sup>+2<i>x</i>-3的图像进行求解;注意到4=2<sup>2</sup>,也可以考虑将(<i>x</i>+1)<sup>2</sup>≥4整理为(<i>x</i>+1)<sup>2</sup>-4≥0,并使用平方差公式,即(<i>x</i>+1)<sup>2</sup>-2<sup>2</sup>≥0,得到(<i>x</i>+3)(<i>x</i>-1)≥0,此时可以借助上面的结论直接求解.下面我们将使用后一种方法进行求解.' |
| | | ], |
| | | thinkThree:[ |
| | | '利润=(销售单价-成本单价)×销售量.降价过程中,单价降低能够使销售量变大,但也使销售单价与成本单价的差减小,所以降价的范围应保证利润不低于促销前.' |
| | | ], |
| | | isShowAnswer: false, |
| | | isShowAnswerOne: false, |
| | | ...showObj |
| | | }; |
| | | }, |
| | | mounted() { }, |
| | | methods: {}, |
| | | mounted() { |
| | | console.log(2, this); |
| | | }, |
| | | methods: { |
| | | openDialog(queryData) { |
| | | this.thinkData = queryData |
| | | this.thinkingDialog = !this.thinkingDialog |
| | | }, |
| | | closeDialog() { |
| | | this.showIndex = 0 |
| | | }, |
| | | changeNext() { |
| | | if (this.showIndex < this.thinkData.length - 1) this.showIndex = this.showIndex + 1 |
| | | } |
| | | }, |
| | | }; |
| | | </script> |
| | | |
| | |
| | | top: 0; |
| | | width: 140px; |
| | | } |
| | | |
| | | .question-textarea { |
| | | margin-left: 20px; |
| | | width: 94%; |
| | | border-color:#DCDFE6; |
| | | border-color: #DCDFE6; |
| | | } |
| | | |
| | | .table-answer-box { |
| | | math { |
| | | width: max-content; |
| | | height: 36px; |
| | | } |
| | | } |
| | | |
| | | li { |
| | | list-style: none; |
| | | } |
| | | </style> |
| | |
| | | <template> |
| | | <div class="chapter" num="3"> |
| | | <div class="chapter" num="4"> |
| | | <!-- 第三单元首页 --> |
| | | <div class="page-box" page="74"> |
| | | <div v-if="showPageList.indexOf(74) > -1"> |
| | |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p><span |
| | | class="zt-ls"><b>例1</b></span> 我国要建设现代化产业体系,推动制造业高端化发展.李平制作了6个机械零件,它们的直径如表3-2所示.请用函数的概念描述李平制作这批机械零件的直径<i>y</i>(<i>mm</i> |
| | | )与零件的标号<i>x</i>的函数关系.</p> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span |
| | | class="zt-ls"><b>例1</b></span> 我国要建设现代化产业体系,推动制造业高端化发展.李平制作了6个机械零件,它们的直径如表3-2所示.请用函数的概念描述李平制作这批机械零件的直径<i>y</i>(<i>mm</i> |
| | | )与零件的标号<i>x</i>的函数关系. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer0 = !isShowAnswer0"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="img">表3-2</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0082-1.jpg" /></p> |
| | | <p><span class="zt-ls"><b>解</b></span> |
| | | <p v-if="isShowAnswer0" > |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 设<i>x</i>表示零件的标号,<i>y</i>表示零件的直径,由表3-2,{1,2,3,4,5,6}中的任一数,<i>y</i>都有任一确定的值与它对应,所以表3-2确定了<i>y</i>与<i>x</i>的函数关系,其定义域为{1,2,3,4,5,6},值域为{13.40,13.50,13.55,13.60,13.65,13.70}. |
| | | </p> |
| | | <p><span |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span |
| | | class="zt-ls"><b>例2</b></span> 已知函数<i>f</i>(<i>x</i>)=3<i>x</i><sup>2</sup>-1.当自变量<i>x</i>为-1,0,1,<i>a</i>时,求它们所对应的函数值. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer1 = !isShowAnswer1"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p><span class="zt-ls"><b>解</b></span> <i>f</i>(-1)=3×(-1)<sup>2</sup>-1=3-1=2,</p> |
| | | <p> <i>f</i>(0)=3×0<sup>2</sup>-1=0-1=-1,</p> |
| | | <p> <i>f</i>(1)=3×1<sup>2</sup>-1=3-1=2,</p> |
| | | <p> <i>f</i>(<i>a</i>)=3×<i>a</i><sup>2</sup>-1=3<i>a</i><sup>2</sup>-1.</p> |
| | | <div v-if="isShowAnswer1" > |
| | | <p><span class="zt-ls"><b>解</b></span> <i>f</i>(-1)=3×(-1)<sup>2</sup>-1=3-1=2,</p> |
| | | <p> <i>f</i>(0)=3×0<sup>2</sup>-1=0-1=-1,</p> |
| | | <p> <i>f</i>(1)=3×1<sup>2</sup>-1=3-1=2,</p> |
| | | <p> <i>f</i>(<i>a</i>)=3×<i>a</i><sup>2</sup>-1=3<i>a</i><sup>2</sup>-1.</p> |
| | | </div> |
| | | <div class="fieldset"> |
| | | <p><b>相关链接</b></p> |
| | | <p class="block">魔方是由6个不同颜色的面组成的正方体,它可组成约4 325亿亿种不同颜色的组合,其最佳复原魔方颜色组合的方法是用数学方法研究出来的.</p> |
| | |
| | | </div> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0082-2.jpg" /></p> |
| | | <p class="img">图3-2</p> |
| | | <p><span class="zt-ls"><b>例3</b></span> 如图3-2所示,一个边长是<i>a</i>的正方体,体积是<i>V</i>,写出体积<i>V</i> 随边长<i>a</i> |
| | | 变化的函数关系式,并指出函数的自变量和定义域.</p> |
| | | <p><span class="zt-ls"><b>解</b></span> 体积<i>V</i> 随边长<i>a</i>变化的函数关系式是</p> |
| | | <p class="center"><i>V</i>=<i>a</i><sup>3</sup>(<i>a</i>>0).</p> |
| | | <p>其中<i>a</i>是自变量,定义域为{<i>a</i>|<i>a</i>>0}.</p> |
| | | <p> |
| | | <span> |
| | | <span class="zt-ls"><b>例3</b></span> 如图3-2所示,一个边长是<i>a</i>的正方体,体积是<i>V</i>,写出体积<i>V</i> 随边长<i>a</i> |
| | | 变化的函数关系式,并指出函数的自变量和定义域. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer2 = !isShowAnswer2"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer2" > |
| | | <p><span class="zt-ls"><b>解</b></span> 体积<i>V</i> 随边长<i>a</i>变化的函数关系式是</p> |
| | | <p class="center"><i>V</i>=<i>a</i><sup>3</sup>(<i>a</i>>0).</p> |
| | | <p>其中<i>a</i>是自变量,定义域为{<i>a</i>|<i>a</i>>0}.</p> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /></p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[78] ? questionData[78][2] : []" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | |
| | | </mfrac> |
| | | </math>的函数值<i>f</i>(0),因为<i>f</i>(0)无意义,因此,它的定义域是{<i>x</i>|<i>x</i>≠0}.在实际问题中,函数的定义域通常由问题的实际背景所决定.如例3中的函数<i>V</i>=<i>a</i><sup>3</sup>,由于<i>a</i>是正方体的边长,所以函数的定义域为<i>A</i>={<i>a</i>|<i>a</i>>0}. |
| | | </p> |
| | | <p><span |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span |
| | | class="zt-ls"><b>例4</b></span> 就业是最基本的民生,小凯通过自主创办奶品店实现职业发展.为促销自制酸奶,每瓶酸奶的价格是3.5元,每位顾客最多只能购买50瓶.假设某人购买这种酸奶<i>x</i>瓶,应付款<i>y</i>元.那么<i>y</i>(元)是<i>x</i>(瓶)的函数吗?如果是,请写出函数的定义域、对应关系和值域;如果不是,请说明理由. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer3 = !isShowAnswer3"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p><span class="zt-ls"><b>解</b></span> |
| | | <i>x</i>的取值范围是数集<i>A</i>={<i>x</i>|<i>x</i>≤50,<i>x</i>∈<b>N</b>},<i>y</i>的取值范围是数集<i>B</i>={<i>y</i>|<i>y</i>=3.5<i>x</i>,<i>x</i>≤50,且<i>x</i>∈<b>N</b>}.对于集合<i>A</i>中的任一个数<i>x</i>,按照对应关系,在集合<i>B</i>中都有唯一确定的值与之对应,所以应付款<i>y</i>是购买数量<i>x</i>的函数. |
| | | </p> |
| | | <p> |
| | | 函数的定义域是{<i>x</i>|<i>x</i>≤50,<i>x</i>∈<b>N</b>},对应关系是<i>y</i>=3.5<i>x</i>,值域是{<i>y</i>|<i>y</i>=3.5<i>x</i>,<i>x</i>≤50,且<i>x</i>∈<b>N</b>}. |
| | | </p> |
| | | <p> |
| | | 例4中函数的定义域为什么是{<i>x</i>|<i>x</i>≤50,<i>x</i>∈<b>N</b>},而不是{<i>x</i>|<i>x</i>∈<b>R</b>}?这是因为此函数的定义域考虑了函数自变量取值的客观实际背景. |
| | | </p> |
| | | <div v-if="isShowAnswer3" > |
| | | <p><span class="zt-ls"><b>解</b></span> |
| | | <i>x</i>的取值范围是数集<i>A</i>={<i>x</i>|<i>x</i>≤50,<i>x</i>∈<b>N</b>},<i>y</i>的取值范围是数集<i>B</i>={<i>y</i>|<i>y</i>=3.5<i>x</i>,<i>x</i>≤50,且<i>x</i>∈<b>N</b>}.对于集合<i>A</i>中的任一个数<i>x</i>,按照对应关系,在集合<i>B</i>中都有唯一确定的值与之对应,所以应付款<i>y</i>是购买数量<i>x</i>的函数. |
| | | </p> |
| | | <p> |
| | | 函数的定义域是{<i>x</i>|<i>x</i>≤50,<i>x</i>∈<b>N</b>},对应关系是<i>y</i>=3.5<i>x</i>,值域是{<i>y</i>|<i>y</i>=3.5<i>x</i>,<i>x</i>≤50,且<i>x</i>∈<b>N</b>}. |
| | | </p> |
| | | <p> |
| | | 例4中函数的定义域为什么是{<i>x</i>|<i>x</i>≤50,<i>x</i>∈<b>N</b>},而不是{<i>x</i>|<i>x</i>∈<b>R</b>}?这是因为此函数的定义域考虑了函数自变量取值的客观实际背景. |
| | | </p> |
| | | </div> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0083-2.jpg" /></p> |
| | | <p class="img">图3-3</p> |
| | | <p><span |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span |
| | | class="zt-ls"><b>例5</b></span> 如图3-3所示,在矩形<i>ABCD</i>中,<i>AB</i>的长度是<i>x</i>(m),<i>BC</i>的长度是(12-<i>x</i>)(m),矩形<i>ABCD</i>的面积是<i>y</i>(<i>m</i><sup>2</sup>),则<i>y</i>与<i>x</i>的对应关系是<i>y</i>=<i>x</i>(12-<i>x</i>),求该函数的定义域. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer4 = !isShowAnswer4"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | <span class="btn-box" @click="openDialog(thinkTwo)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
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| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="block"><span |
| | | class="zt-ls2"><b>分析</b></span> 因为<i>AB</i>的长度为<i>x</i>(m),<i>BC</i>的长度为(12-<i>x</i>)(m),所以必须满足<i>x</i>>0且12-<i>x</i>>0才有实际意义. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 073 --> |
| | | <div class="page-box" page="80"> |
| | | <div v-if="showPageList.indexOf(80) > -1"> |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第三单元 函数</p> |
| | | </li> |
| | | <li> |
| | | <p><span>073</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p><span class="zt-ls"><b>解</b></span> 要使函数<i>y</i>=<i>x</i>(12-<i>x</i>)有实际意义,必须满足<math display="0"> |
| | | <p v-if="isShowAnswer4" > |
| | | <span class="zt-ls"><b>解</b></span> 要使函数<i>y</i>=<i>x</i>(12-<i>x</i>)有实际意义,必须满足<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>解得0<<i>x</i><12.所以这个函数的定义域是{<i>x</i>|0<<i>x</i><12}.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 073 --> |
| | | <div class="page-box" page="80"> |
| | | <div v-if="showPageList.indexOf(80) > -1"> |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第三单元 函数</p> |
| | | </li> |
| | | <li> |
| | | <p><span>073</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p><span class="zt-ls"><b>例6</b></span> 求下列函数的定义域.</p> |
| | | <p>(1) <math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <p class="p-btn" > |
| | | <span> |
| | | (1) <math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>7</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>;(2)<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msqrt> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </msqrt> |
| | | </math>;</p> |
| | | <p>(3) <math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msqrt> |
| | | <mn>4</mn> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>8</mn> |
| | | </msqrt> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>.</p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 要使该函数有意义,必须满足</p> |
| | | <p class="center">4<i>x</i>+7≠0,</p> |
| | | <p>解得</p> |
| | | <math display="block"> |
| | | <mi>x</mi> |
| | | <mo>≠</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>7</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p>所以函数<i>f</i>(<i>x</i>)的定义域是<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mo stretchy="false">|</mo> |
| | | </mrow> |
| | | <mi>x</mi> |
| | | <mo>≠</mo> |
| | | <mo>−</mo> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>7</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">}</mo> |
| | | </mrow> |
| | | </math>.</p> |
| | | <p>(2) 要使该函数有意义,必须满足</p> |
| | | <p class="center"><i>x</i>-3≥0,</p> |
| | | <p>解得 <i>x</i>≥3.</p> |
| | | <p>所以函数<i>f</i>(<i>x</i>)的定义域是{<i>x</i>|<i>x</i>≥3}.</p> |
| | | <p>(3) 要使该函数有意义,必须满足</p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>8</mn> |
| | | <mo>≥</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>; |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer5 = !isShowAnswer5"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer5" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 要使该函数有意义,必须满足</p> |
| | | <p class="center">4<i>x</i>+7≠0,</p> |
| | | <p>解得</p> |
| | | <math display="block"> |
| | | <mi>x</mi> |
| | | <mo>≠</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>7</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p>所以函数<i>f</i>(<i>x</i>)的定义域是<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mo stretchy="false">|</mo> |
| | | </mrow> |
| | | <mi>x</mi> |
| | | <mo>≠</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>7</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">}</mo> |
| | | </mrow> |
| | | </math>.</p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | <span> |
| | | (2)<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msqrt> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </msqrt> |
| | | </math>; |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer6 = !isShowAnswer6"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer6" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(2) 要使该函数有意义,必须满足</p> |
| | | <p class="center"><i>x</i>-3≥0,</p> |
| | | <p>解得 <i>x</i>≥3.</p> |
| | | <p>所以函数<i>f</i>(<i>x</i>)的定义域是{<i>x</i>|<i>x</i>≥3}.</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span> |
| | | (3) <math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msqrt> |
| | | <mn>4</mn> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>8</mn> |
| | | </msqrt> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mo>≠</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math> |
| | | <p>解得</p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>x</mi> |
| | | <mo>≥</mo> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>x</mi> |
| | | <mo>≠</mo> |
| | | <mn>3.</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math> |
| | | <p>所以函数<i>f</i>(<i>x</i>)的定义域是{<i>x</i>|<i>x</i>≥-2且<i>x</i>≠3}.</p> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer7 = !isShowAnswer7"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer7" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(3) 要使该函数有意义,必须满足</p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>4</mn> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>8</mn> |
| | | <mo>≥</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mo>≠</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math> |
| | | <p>解得</p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>x</mi> |
| | | <mo>≥</mo> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>x</mi> |
| | | <mo>≠</mo> |
| | | <mn>3.</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math> |
| | | <p>所以函数<i>f</i>(<i>x</i>)的定义域是{<i>x</i>|<i>x</i>≥-2且<i>x</i>≠3}.</p> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /></p> |
| | | <div class="bj" > |
| | | <examinations :cardList="questionData[80]" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | |
| | | <p>我们知道,上一节“观察思考”中的3个情境都涉及变量之间的函数关系.情境1中,销售收入<i>y</i>(元)与销售量<i>x</i>(kg )的函数关系是<i>y</i>=6<i>x</i>,0≤<i>x</i>≤2 |
| | | 000,这种表示函数关系的方法称为解析法;情境2中,用表格表示了发射卫星的颗数<i>y</i>与年份<i>x</i>的函数关系,这种表示函数关系的方法称为列表法;情境3中,用图像表示了气温<i>Q</i>与时间<i>t</i>的函数关系,这种表示函数关系的方法称为图像法. |
| | | </p> |
| | | <p><span class="zt-ls"><b>例1</b></span> 某辆汽车以30 km/<i>h</i> 的速度匀速直线行驶,用解析法表示汽车行驶的路程<i>s</i>(km |
| | | )与时间<i>t</i>(<i>h</i>)之间的对应关系.</p> |
| | | <p><span class="zt-ls"><b>解</b></span> 这个函数的定义域是{<i>t</i>|<i>t</i>≥0}.</p> |
| | | <p>用解析法可将这个函数表示为<i>s</i>=30<i>t</i>,<i>t</i>≥0.</p> |
| | | <p>用解析法表示函数关系,能够准确、完整地反映两个变量之间的关系.</p> |
| | | <p><span class="zt-ls"><b>例2</b></span> 近年我国快递业务量迅速增长,从2017年至2021年,每年的快递业务量情况如表3-4所示(注:引自国家统计局数据).</p> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例1</b></span> 某辆汽车以30 km/<i>h</i> 的速度匀速直线行驶,用解析法表示汽车行驶的路程<i>s</i>(km |
| | | )与时间<i>t</i>(<i>h</i>)之间的对应关系. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer8 = !isShowAnswer8"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer8" > |
| | | <p><span class="zt-ls"><b>解</b></span> 这个函数的定义域是{<i>t</i>|<i>t</i>≥0}.</p> |
| | | <p>用解析法可将这个函数表示为<i>s</i>=30<i>t</i>,<i>t</i>≥0.</p> |
| | | <p>用解析法表示函数关系,能够准确、完整地反映两个变量之间的关系.</p> |
| | | </div> |
| | | <p> |
| | | <span> |
| | | <span class="zt-ls"><b>例2</b></span> 近年我国快递业务量迅速增长,从2017年至2021年,每年的快递业务量情况如表3-4所示(注:引自国家统计局数据). |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer9 = !isShowAnswer9"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="img">表3-4</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0087-2.jpg" /></p> |
| | | <p>表3-4清晰地反映了年份与当年快递业务量(亿件)之间的对应关系.在实际生活中,用列表法表示变量之间对应关系的例子还有很多.例如,记录某人每天的消费情况、单位职工的每月薪资收入、银行使用的存款“利息表”等.</p> |
| | | <p v-if="isShowAnswer9" >表3-4清晰地反映了年份与当年快递业务量(亿件)之间的对应关系.在实际生活中,用列表法表示变量之间对应关系的例子还有很多.例如,记录某人每天的消费情况、单位职工的每月薪资收入、银行使用的存款“利息表”等.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p>观察上一节“观察思考”中的情境3,我们发现用图像法表示函数关系时能直观形象地表示出函数的局部变化规律,进而可以预测它的整体变化趋势.但是我们并不能作出所有函数的图像.</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0088-1.jpg" /></p> |
| | | <p class="img">图3-4</p> |
| | | <p><span |
| | | class="zt-ls"><b>例3</b></span> 使用环保毛巾替代一次性纸巾,是倡导低碳环保生活的一种方式.某便民超市促销某种小毛巾,每条售价4元,每人限购5条.若顾客购买<i>x</i>条小毛巾需要付款<i>y</i>元,试用图像法表示函数<i>y</i>=<i>f</i>(<i>x</i>). |
| | | </p> |
| | | <p><span class="zt-ls"><b>解</b></span> 函数<i>y</i>=<i>f</i>(<i>x</i>)的定义域是{1,2,3,4,5},用图像法可将这个函数表示为图3-4.</p> |
| | | <div v-if="isShowAnswer9" > |
| | | <p>观察上一节“观察思考”中的情境3,我们发现用图像法表示函数关系时能直观形象地表示出函数的局部变化规律,进而可以预测它的整体变化趋势.但是我们并不能作出所有函数的图像.</p> |
| | | </div> |
| | | <p> |
| | | 函数的图像既可以是离散的点,也可以是线段、直线、折线、连续的曲线等.在初中,我们用列表、描点、连线的方法画出了正比例函数、反比例函数、一次函数和二次函数的图像.图像法也被大量用于各类数据统计中.例如,GDP(国内生产总值)每年的增长情况、居民消费价格每季度的增长情况、全国人口数量每年的变化情况等. |
| | | <span> |
| | | <span |
| | | class="zt-ls"><b>例3</b></span> 使用环保毛巾替代一次性纸巾,是倡导低碳环保生活的一种方式.某便民超市促销某种小毛巾,每条售价4元,每人限购5条.若顾客购买<i>x</i>条小毛巾需要付款<i>y</i>元,试用图像法表示函数<i>y</i>=<i>f</i>(<i>x</i>). |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer10 = !isShowAnswer10"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p><span class="zt-ls"><b>例4</b></span> 一艘军舰与某海港相距135 n mile(1 n mile ≈1.852 km ),如果军舰以45 n mile/h 的速度向海港前行,则3 |
| | | h后可到达海港.假设这艘军舰出发t(h)后,与海港的距离是s(n mile).</p> |
| | | <p>(1) 用解析法表示函数<i>s</i>=<i>f</i>(<i>t</i>);</p> |
| | | <p>(2) 用图像法表示函数<i>s</i>=<i>f</i>(<i>t</i>).</p> |
| | | <p class="block"><span |
| | | class="zt-ls2"><b>分析</b></span> 计算该军舰从出发地驶入海港所需要的时间,就可得到函数<i>s</i>=<i>f</i>(<i>t</i>)的定义域.用解析法表示函数后,再画出函数的图像. |
| | | <div v-if="isShowAnswer10" > |
| | | <p><span class="zt-ls"><b>解</b></span> 函数<i>y</i>=<i>f</i>(<i>x</i>)的定义域是{1,2,3,4,5},用图像法可将这个函数表示为图3-4.</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0088-1.jpg" /></p> |
| | | <p class="img">图3-4</p> |
| | | <p> |
| | | 函数的图像既可以是离散的点,也可以是线段、直线、折线、连续的曲线等.在初中,我们用列表、描点、连线的方法画出了正比例函数、反比例函数、一次函数和二次函数的图像.图像法也被大量用于各类数据统计中.例如,GDP(国内生产总值)每年的增长情况、居民消费价格每季度的增长情况、全国人口数量每年的变化情况等. |
| | | </p> |
| | | </div> |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" class="iframe-box"></iframe> |
| | | <p> |
| | | <span> |
| | | <span class="zt-ls"><b>例4</b></span> 一艘军舰与某海港相距135 n mile(1 n mile ≈1.852 km ),如果军舰以45 n mile/h 的速度向海港前行,则3 |
| | | h后可到达海港.假设这艘军舰出发t(h)后,与海港的距离是s(n mile). |
| | | </span> |
| | | <span class="btn-box" @click="openDialog(thinkThree)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
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| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 因为该军舰从出发地驶入海港需要用时<math display="0"> |
| | | <mfrac> |
| | | <mn>135</mn> |
| | | <mn>45</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>3</mn> |
| | | <mo>(</mo> |
| | | <mi>h</mi> |
| | | <mo>)</mo> |
| | | </math>,所以函数的定义域为{<i>t</i>|0≤<i>t</i>≤3}.</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0088-3.jpg" /></p> |
| | | <p class="img">图3-5</p> |
| | | <p class="p-btn" > |
| | | <span> |
| | | (1) 用解析法表示函数<i>s</i>=<i>f</i>(<i>t</i>); |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer11 = !isShowAnswer11"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer11" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 因为该军舰从出发地驶入海港需要用时<math display="0"> |
| | | <mfrac> |
| | | <mn>135</mn> |
| | | <mn>45</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>3</mn> |
| | | <mo>(</mo> |
| | | <mi>h</mi> |
| | | <mo>)</mo> |
| | | </math>,所以函数的定义域为{<i>t</i>|0≤<i>t</i>≤3}. |
| | | </p> |
| | | <p>又因为该军舰出发<i>t</i>(<i>h</i>)后,行驶的路程为45<i>t n mile</i> ,这时该军舰与海港的距离为(135-45<i>t</i>) <i>n mile</i> .</p> |
| | | <p>所以,用解析法可将函数<i>s</i>=<i>f</i>(<i>t</i>)表示为</p> |
| | | <p class="center"><i>s</i>=-45<i>t</i>+135,0≤<i>t</i>≤3.</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(2) 用图像法表示函数<i>s</i>=<i>f</i>(<i>t</i>).</span> |
| | | <span class="btn-box" @click="isShowAnswer12 = !isShowAnswer12"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer12" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(2) 函数<i>s</i>=<i>f</i>(<i>t</i>)是一次函数,用图像法可将函数表示为图3-5.</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0088-3.jpg" /></p> |
| | | <p class="img">图3-5</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p>又因为该军舰出发<i>t</i>(<i>h</i>)后,行驶的路程为45<i>t n mile</i> ,这时该军舰与海港的距离为(135-45<i>t</i>) <i>n mile</i> .</p> |
| | | <p>所以,用解析法可将函数<i>s</i>=<i>f</i>(<i>t</i>)表示为</p> |
| | | <p class="center"><i>s</i>=-45<i>t</i>+135,0≤<i>t</i>≤3.</p> |
| | | <p>(2) 函数<i>s</i>=<i>f</i>(<i>t</i>)是一次函数,用图像法可将函数表示为图3-5.</p> |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"><img class="img-gn2" alt="" src="../../assets/images/hzjl.jpg" /></p> |
| | |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math></p> |
| | | <p>(1) 求<i>f</i>(-5),<i>f</i>(4)的值;</p> |
| | | <p class="p-btn" > |
| | | <span> |
| | | (1) 求<i>f</i>(-5),<i>f</i>(4)的值; |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer13 = !isShowAnswer13"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer13" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 因为-5<0,所以<i>f</i>(-5)=-5+2=-3.</p> |
| | | <p>因为4>0,所以 <i>f</i>(4)=4<sup>2</sup>-3=13.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p>(2) 求<i>f</i>(<i>f</i>(-1))的值.</p> |
| | | <p class="p-btn" > |
| | | <span>(2) 求<i>f</i>(<i>f</i>(-1))的值.</span> |
| | | <span class="btn-box" @click="isShowAnswer14 = !isShowAnswer14"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer14"> |
| | | <p> <span class="zt-ls"><b>解</b></span>(2) 因为-1<0,所以<i>f</i>(-1)=-1+2=1.</p> |
| | | <p>又因为1>0,所以<i>f</i>(<i>f</i>(-1))=<i>f</i>(1)=1<sup>2</sup>-3=-2.</p> |
| | | </div> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"><img class="img-gn1" alt="" src="../../assets/images/tbts.jpg" /></p> |
| | |
| | | 分段函数是一个函数,不能把它看成几个函数,只是在同一个函数的定义域内,不同的取值范围内对应不同的函数关系.它的定义域是各个解析式的自变量取值集合的并集,值域也是各个解析式的函数值集合的并集.它的图像也比较特殊,有时图像是不连续的. |
| | | </p> |
| | | </div> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 因为-5<0,所以<i>f</i>(-5)=-5+2=-3.</p> |
| | | <p>因为4>0,所以 <i>f</i>(4)=4<sup>2</sup>-3=13.</p> |
| | | <p>(2) 因为-1<0,所以<i>f</i>(-1)=-1+2=1.</p> |
| | | <p>又因为1>0,所以<i>f</i>(<i>f</i>(-1))=<i>f</i>(1)=1<sup>2</sup>-3=-2.</p> |
| | | <p><span |
| | | <p> |
| | | <span |
| | | class="zt-ls"><b>例2</b></span> 我国是用电量最大的国家,国家发出节能减排的号召,鼓励居民节约用电,2019年国家对居民每月用电量进行划分,电价施行“分档递增”.某城市居民每月用电计费价格如表3-7所示.假设这个城市的某居民某月用电量是<i>x</i>(kW·h),需支付电费<i>y</i>(元). |
| | | <span class="btn-box" @click="openDialog(thinkFour)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
| | | d="M3771.2-14311.889a2.356,2.356,0,0,1-1.727-.626c-.027-.054-.053-.1-.079-.148l0-.007c-.123-.224-.2-.371-.076-.629a.869.869,0,0,1,.784-.471.205.205,0,0,1,.158.079.205.205,0,0,0,.158.079.187.187,0,0,0,.038.1.143.143,0,0,0,.117.05h.158a.573.573,0,0,0,.471.158,2.2,2.2,0,0,0,.916-.3l.023-.011a.572.572,0,0,1,.471-.158.575.575,0,0,1,.626.626.526.526,0,0,1,.036.409.664.664,0,0,1-.349.375A3.582,3.582,0,0,1,3771.2-14311.889Zm-1.885-1.723h-.155a.718.718,0,0,1-.784-.63.38.38,0,0,1-.021-.3.976.976,0,0,1,.492-.485l4.86-1.252a1.047,1.047,0,0,1,.784.626c.151.3-.128.61-.471.784l-4.705,1.256Zm-.155-1.885H3769a.716.716,0,0,1-.784-.626c-.149-.3.129-.611.471-.784l4.234-1.1v-.158l-.021.007a7.808,7.808,0,0,1-1.861.31,5.3,5.3,0,0,1-3.137-.942,5.789,5.789,0,0,1-2.666-4.076,6.421,6.421,0,0,1,1.256-5.018,7.038,7.038,0,0,1,2.194-1.568,7.848,7.848,0,0,1,2.666-.472,6.43,6.43,0,0,1,2.979.784,4.958,4.958,0,0,1,2.2,2.194,5.522,5.522,0,0,1,.313,5.177,13.113,13.113,0,0,1-1.256,1.882l-.313.313a2.156,2.156,0,0,0-.78,1.244l0,.012a1.731,1.731,0,0,1-1.727,1.723l-.313.158-3.292.939Zm1.256-6.271v1.256h1.41v-1.256Zm.784-4.234c.718,0,1.1.271,1.1.784a.925.925,0,0,1-.316.783l-.468.156a2.235,2.235,0,0,0-.63.471l-.012.024a2.2,2.2,0,0,0-.3.918v.155h1.1v-.155a1.2,1.2,0,0,1,.313-.629.543.543,0,0,0,.315-.153c.007,0,.315,0,.315-.16a1.226,1.226,0,0,0,.626-.626,2.277,2.277,0,0,0,.313-1.1,1.409,1.409,0,0,0-.626-1.252,2.337,2.337,0,0,0-1.569-.471,2.258,2.258,0,0,0-2.507,2.353l1.252.154A1.121,1.121,0,0,1,3771.2-14326Zm-6.51,9.645a.769.769,0,0,1-.549-.237.772.772,0,0,1-.235-.549.772.772,0,0,1,.235-.548l.939-.939a.781.781,0,0,1,.55-.234.772.772,0,0,1,.547.234.772.772,0,0,1,.238.549.772.772,0,0,1-.238.549l-.939.938A.769.769,0,0,1,3764.686-14316.356Zm13.174-.157a.774.774,0,0,1-.549-.234l-.943-.942a.678.678,0,0,1-.233-.47.678.678,0,0,1,.233-.47.774.774,0,0,1,.549-.234.774.774,0,0,1,.549.234l.942.939a.427.427,0,0,1,.228.324.74.74,0,0,1-.228.618A.774.774,0,0,1,3777.859-14316.514Zm2.9-6.351h-1.414c-.469-.158-.784-.474-.784-.784a.743.743,0,0,1,.784-.784h1.414a.743.743,0,0,1,.784.784A.743.743,0,0,1,3780.761-14322.864Zm-17.566-.158h-1.41c-.469-.157-.784-.473-.784-.784a.743.743,0,0,1,.784-.784h1.41a.743.743,0,0,1,.784.784A.743.743,0,0,1,3763.195-14323.022Zm13.861-5.723a.759.759,0,0,1-.529-.237.776.776,0,0,1-.235-.549.772.772,0,0,1,.235-.549l.939-.938a.44.44,0,0,1,.413-.238.759.759,0,0,1,.529.238.772.772,0,0,1,.235.549.772.772,0,0,1-.235.548l-.942.939A.435.435,0,0,1,3777.055-14328.745Zm-11.429,0a.776.776,0,0,1-.55-.237l-.939-1.1a.678.678,0,0,1-.235-.469.678.678,0,0,1,.235-.47.772.772,0,0,1,.549-.238.772.772,0,0,1,.549.238l.939,1.1a.675.675,0,0,1,.238.47.675.675,0,0,1-.238.47A.767.767,0,0,1,3765.626-14328.745Zm5.724-2.273a.743.743,0,0,1-.784-.785v-1.413c.157-.469.473-.784.784-.784a.743.743,0,0,1,.784.784v1.413A.743.743,0,0,1,3771.35-14331.019Z" |
| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="img">表3-7 某城市居民每月用电计费价格表</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0091-1.jpg" /></p> |
| | | <p>(1) 用解析法表示<i>y</i>与<i>x</i>的函数关系,并画出函数的图像.</p> |
| | | <p>(2) 如果李某家10月的用电量是180 kW·h ,那么他家应该支付电费多少?</p> |
| | | <p>(3) 如果周某家12月支付电费294.26元,那么他家这个月的用电量是多少?</p> |
| | | <p class="block"><span |
| | | class="zt-ls2"><b>分析</b></span> 首先需明确这个函数的定义域.由于居民用电量不同,其收费标准也不同,所以这是分段函数.其次要厘清自变量<i>x</i>在不同的取值范围内与因变量<i>y</i>之间的对应关系,并列出相应的解析式来解决相关问题. |
| | | <p class="p-btn" > |
| | | <span>(1) 用解析法表示<i>y</i>与<i>x</i>的函数关系,并画出函数的图像.</span> |
| | | <span class="btn-box" @click="isShowAnswer15 = !isShowAnswer15"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 函数<i>y</i>=<i>f</i>(<i>x</i>)的定义域是{<i>x</i>|<i>x</i>≥0}.</p> |
| | | <p>当0≤<i>x</i>≤200时,<i>y</i>与<i>x</i>的对应关系是<i>y</i>=0.52<i>x</i>;</p> |
| | | <p>当200<<i>x</i>≤400时,<i>y</i>与<i>x</i>的对应关系是</p> |
| | | <p class="center"><i>y</i>=0.52×200+0.57(<i>x</i>-200)=0.57<i>x</i>-10;</p> |
| | | <p>当<i>x</i>>400时,<i>y</i>与<i>x</i>的对应关系是</p> |
| | | <p><i>y</i>=0.52×200+0.57×200+0.82(<i>x</i>-400)=0.82<i>x</i>-110.</p> |
| | | <p>用解析法表示<i>y</i>与<i>x</i>的函数关系如下.</p> |
| | | <math display="block"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>0.52</mn> |
| | | <mi>x</mi> |
| | | <mo>,</mo> |
| | | <mn>0</mn> |
| | | <mo>≤</mo> |
| | | <mi>x</mi> |
| | | <mo>≤</mo> |
| | | <mn>200</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>0.57</mn> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>10</mn> |
| | | <mo>,</mo> |
| | | <mn>200</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>≤</mo> |
| | | <mn>400</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>0.82</mn> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>110</mn> |
| | | <mo>,</mo> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>400.</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0092-1.jpg" /></p> |
| | | <p class="img">图3-7</p> |
| | | <div v-if="isShowAnswer15" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 函数<i>y</i>=<i>f</i>(<i>x</i>)的定义域是{<i>x</i>|<i>x</i>≥0}.</p> |
| | | <p>当0≤<i>x</i>≤200时,<i>y</i>与<i>x</i>的对应关系是<i>y</i>=0.52<i>x</i>;</p> |
| | | <p>当200<<i>x</i>≤400时,<i>y</i>与<i>x</i>的对应关系是</p> |
| | | <p class="center"><i>y</i>=0.52×200+0.57(<i>x</i>-200)=0.57<i>x</i>-10;</p> |
| | | <p>当<i>x</i>>400时,<i>y</i>与<i>x</i>的对应关系是</p> |
| | | <p><i>y</i>=0.52×200+0.57×200+0.82(<i>x</i>-400)=0.82<i>x</i>-110.</p> |
| | | <p>用解析法表示<i>y</i>与<i>x</i>的函数关系如下.</p> |
| | | <math display="block"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>0.52</mn> |
| | | <mi>x</mi> |
| | | <mo>,</mo> |
| | | <mn>0</mn> |
| | | <mo>≤</mo> |
| | | <mi>x</mi> |
| | | <mo>≤</mo> |
| | | <mn>200</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>0.57</mn> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>10</mn> |
| | | <mo>,</mo> |
| | | <mn>200</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>≤</mo> |
| | | <mn>400</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>0.82</mn> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>110</mn> |
| | | <mo>,</mo> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>400.</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0092-1.jpg" /></p> |
| | | <p class="img">图3-7</p> |
| | | <p>这个函数的图像如图3-7所示.</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(2) 如果李某家10月的用电量是180 kW·h ,那么他家应该支付电费多少?</span> |
| | | <span class="btn-box" @click="isShowAnswer16 = !isShowAnswer16"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer16" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(2) 因为<i>x</i>=180<200,<i>y</i>=0.52×180=93.60(元).</p> |
| | | <p>所以,李某家10月应该支付电费93.60元.</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(3) 如果周某家12月支付电费294.26元,那么他家这个月的用电量是多少?</span> |
| | | <span class="btn-box" @click="isShowAnswer17 = !isShowAnswer17"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer17" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(3) 周某家电费是294.26元,由图3-7可估得<i>x</i>>400,因此</p> |
| | | <p class="center">0.82<i>x</i>-110=294.26,</p> |
| | | <p>解得<i>x</i>=493.</p> |
| | | <p>所以,周某家12月的用电量为493 kW·h .</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p>这个函数的图像如图3-7所示.</p> |
| | | <p>(2) 因为<i>x</i>=180<200,<i>y</i>=0.52×180=93.60(元).</p> |
| | | <p>所以,李某家10月应该支付电费93.60元.</p> |
| | | <p>(3) 周某家电费是294.26元,由图3-7可估得<i>x</i>>400,因此</p> |
| | | <p class="center">0.82<i>x</i>-110=294.26,</p> |
| | | <p>解得<i>x</i>=493.</p> |
| | | <p>所以,周某家12月的用电量为493 kW·h .</p> |
| | | |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"><img class="img-gn2" alt="" src="../../assets/images/hzjl.jpg" /></p> |
| | |
| | | 例如,图3-8中函数<i>y</i>=<i>x</i>是<b>R</b>上的增函数,区间(-∞,+∞)是函数<i>y</i>=<i>x</i>的增区间;函数<i>y</i>=-<i>x</i>是<b>R</b>上的减函数,区间(-∞,+∞)是函数<i>y</i>=-<i>x</i>的减区间;函数<i>y</i>=<i>x</i><sup>2</sup>在区间(-∞,0)上是减函数,在区间(0,+∞)上是增函数,区间(-∞,0)和(0,+∞)分别是函数<i>y</i>=<i>x</i><sup>2</sup>的减区间、增区间. |
| | | </p> |
| | | <p><span class="zt-ls"><b>例1</b></span> 图3-11是函数<i>y</i>=<i>f</i>(<i>x</i>),<i>x</i>∈[-1,8]的图像,根据图像回答下列问题.</p> |
| | | <p>(1) 当<i>x</i>取何值时,函数值最大,最大值是多少?当<i>x</i>取何值时,函数值最小,最小值是多少?</p> |
| | | <p>(2) 说明该函数的单调区间及在每一个区间上的单调性.</p> |
| | | <p class="p-btn" > |
| | | <span>(1) 当<i>x</i>取何值时,函数值最大,最大值是多少?当<i>x</i>取何值时,函数值最小,最小值是多少?</span> |
| | | <span class="btn-box" @click="isShowAnswer18 = !isShowAnswer18"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p v-if="isShowAnswer18" ><span class="zt-ls"><b>解</b></span>(1) 由图可知,当<i>x</i>=2时,函数值最大,最大值是3;当<i>x</i>=6时,函数值最小,最小值是-3.</p> |
| | | <p class="p-btn" > |
| | | <span>(2) 说明该函数的单调区间及在每一个区间上的单调性.</span> |
| | | <span class="btn-box" @click="isShowAnswer19 = !isShowAnswer19"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0097-3.jpg" /></p> |
| | | <p class="img">图3-11</p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 由图可知,当<i>x</i>=2时,函数值最大,最大值是3;当<i>x</i>=6时,函数值最小,最小值是-3.</p> |
| | | <p>(2) |
| | | <p v-if="isShowAnswer19" > |
| | | <span class="zt-ls"><b>解</b></span> |
| | | (2) |
| | | 函数<i>y</i>=<i>f</i>(<i>x</i>)的单调区间有[-1,2],[2,6],[6,8].函数<i>y</i>=<i>f</i>(<i>x</i>)在区间[-1,2]和[6,8]上都是增函数,在区间[2,6]上是减函数. |
| | | </p> |
| | | </div> |
| | |
| | | <p class="img">图3-12</p> |
| | | <p><span class="zt-ls"><b>例2</b></span> 二次函数<i>f</i>(<i>x</i>)=-<i>x</i><sup>2</sup>+2<i>x</i>+3的图像如图3-12所示. |
| | | </p> |
| | | <p>(1) 求函数<i>f</i>(<i>x</i>)的对称轴方程、顶点坐标;</p> |
| | | <p>(2) 找出函数<i>f</i>(<i>x</i>)的单调区间;</p> |
| | | <p>(3) 当<i>x</i>∈[2,5]时,求函数<i>f</i>(<i>x</i>)的最大值和最小值.</p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 二次函数<i>y</i>=<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>的对称轴方程是<math |
| | | display="0"> |
| | | <mi>x</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>,顶点坐标是<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <p class="p-btn" > |
| | | <span>(1) 求函数<i>f</i>(<i>x</i>)的对称轴方程、顶点坐标;</span> |
| | | <span class="btn-box" @click="isShowAnswer20 = !isShowAnswer20"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer20" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 二次函数<i>y</i>=<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>的对称轴方程是<math |
| | | display="0"> |
| | | <mi>x</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mrow> |
| | |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>a</mi> |
| | | <mi>c</mi> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,则</p> |
| | | <math display="block"> |
| | | <mtable columnalign="left" columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | </math>,顶点坐标是<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mo>×</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>1,</mn> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>4</mn> |
| | |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mo>×</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>×</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,则</p> |
| | | <math display="block"> |
| | | <mtable columnalign="left" columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mo>×</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>1,</mn> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>a</mi> |
| | | <mi>c</mi> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mo>×</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>×</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mo>×</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>4</mn> |
| | | <mo>.</mo> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | </math> |
| | | <p>因此,函数<i>f</i>(<i>x</i>)的对称轴方程是<i>x</i>=1,顶点坐标是(1,4).</p> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mo>×</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>4</mn> |
| | | <mo>.</mo> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | </math> |
| | | <p>因此,函数<i>f</i>(<i>x</i>)的对称轴方程是<i>x</i>=1,顶点坐标是(1,4).</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(2) 找出函数<i>f</i>(<i>x</i>)的单调区间;</span> |
| | | <span class="btn-box" @click="isShowAnswer21 = !isShowAnswer21"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p v-if="isShowAnswer21" > <span class="zt-ls"><b>解</b></span>(2) 由图像可知,函数<i>f</i>(<i>x</i>)的增区间是(-∞,1],减区间是[1,+∞).</p> |
| | | <p class="p-btn" > |
| | | <span>(3) 当<i>x</i>∈[2,5]时,求函数<i>f</i>(<i>x</i>)的最大值和最小值.</span> |
| | | <span class="btn-box" @click="isShowAnswer22 = !isShowAnswer22"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer22" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(3) 因为[2,5]⫋[1,+∞),且函数在区间[1,+∞)上是减函数,所以当<i>x</i>∈[2,5]时,</p> |
| | | <p>函数<i>f</i>(<i>x</i>)的最大值是<i>f</i>(2)=-2<sup>2</sup>+2×2+3=3,</p> |
| | | <p>函数<i>f</i>(<i>x</i>)的最小值是<i>f</i>(5)=-5<sup>2</sup>+2×5+3=-12.</p> |
| | | </div> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"><img class="img-gn1" alt="" src="../../assets/images/tbts.jpg" /></p> |
| | | </div> |
| | | <p class="block">函数的单调性是对定义域内某个区间而言的.一个函数在其定义域上不一定具有单调性,但是在定义域内的子区间上可能具有单调性,这就是函数单调性的局部性质.</p> |
| | | </div> |
| | | <p>(2) 由图像可知,函数<i>f</i>(<i>x</i>)的增区间是(-∞,1],减区间是[1,+∞).</p> |
| | | <p>(3) 因为[2,5]⫋[1,+∞),且函数在区间[1,+∞)上是减函数,所以当<i>x</i>∈[2,5]时,</p> |
| | | <p>函数<i>f</i>(<i>x</i>)的最大值是<i>f</i>(2)=-2<sup>2</sup>+2×2+3=3,</p> |
| | | <p>函数<i>f</i>(<i>x</i>)的最小值是<i>f</i>(5)=-5<sup>2</sup>+2×5+3=-12.</p> |
| | | <p><span class="zt-ls"><b>例3</b></span> 判断函数<i>f</i>(<i>x</i>)=<i>x</i>+1在(-∞,+∞)上的单调性.</p> |
| | | <p><span class="zt-ls"><b>解</b></span> |
| | | 任取<i>x</i><sub>1</sub>,<i>x</i><sub>2</sub>∈(-∞,+∞),且<i>x</i><sub>1</sub><<i>x</i><sub>2</sub>,那么</p> |
| | | <p class="center"> |
| | | <i>f</i>(<i>x</i><sub>1</sub>)=<i>x</i><sub>1</sub>+1,<i>f</i>(<i>x</i><sub>2</sub>)=<i>x</i><sub>2</sub>+1, |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例3</b></span> 判断函数<i>f</i>(<i>x</i>)=<i>x</i>+1在(-∞,+∞)上的单调性. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer23 = !isShowAnswer23"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p>则</p> |
| | | <p class="center"> |
| | | <i>f</i>(<i>x</i><sub>1</sub>)-<i>f</i>(<i>x</i><sub>2</sub>)=<i>x</i><sub>1</sub>+1-<i>x</i><sub>2</sub>-1=<i>x</i><sub>1</sub>-<i>x</i><sub>2</sub><0, |
| | | </p> |
| | | <p> |
| | | 所以<i>f</i>(<i>x</i><sub>1</sub>)<<i>f</i>(<i>x</i><sub>2</sub>),函数<i>f</i>(<i>x</i>)=<i>x</i>+1在(-∞,+∞)上是增函数. |
| | | </p> |
| | | <p>当<i>k</i>>0时,函数<i>f</i>(<i>x</i>)=<i>kx</i>+<i>b</i>在区间(-∞,+∞)上是增函数,如图3-13(1) |
| | | 所示;当<i>k</i><0时,函数<i>f</i>(<i>x</i>)=<i>kx</i>+<i>b</i>在区间(-∞,+∞)上是减函数,如图3-13(2) 所示.</p> |
| | | <p class="center"><img class="img-b" alt="" src="../../assets/images/0098-5.jpg" /></p> |
| | | <p class="img">图3-13</p> |
| | | <div v-if="isShowAnswer23" > |
| | | <p><span class="zt-ls"><b>解</b></span> |
| | | 任取<i>x</i><sub>1</sub>,<i>x</i><sub>2</sub>∈(-∞,+∞),且<i>x</i><sub>1</sub><<i>x</i><sub>2</sub>,那么</p> |
| | | <p class="center"> |
| | | <i>f</i>(<i>x</i><sub>1</sub>)=<i>x</i><sub>1</sub>+1,<i>f</i>(<i>x</i><sub>2</sub>)=<i>x</i><sub>2</sub>+1, |
| | | </p> |
| | | <p>则</p> |
| | | <p class="center"> |
| | | <i>f</i>(<i>x</i><sub>1</sub>)-<i>f</i>(<i>x</i><sub>2</sub>)=<i>x</i><sub>1</sub>+1-<i>x</i><sub>2</sub>-1=<i>x</i><sub>1</sub>-<i>x</i><sub>2</sub><0, |
| | | </p> |
| | | <p> |
| | | 所以<i>f</i>(<i>x</i><sub>1</sub>)<<i>f</i>(<i>x</i><sub>2</sub>),函数<i>f</i>(<i>x</i>)=<i>x</i>+1在(-∞,+∞)上是增函数. |
| | | </p> |
| | | <p>当<i>k</i>>0时,函数<i>f</i>(<i>x</i>)=<i>kx</i>+<i>b</i>在区间(-∞,+∞)上是增函数,如图3-13(1) |
| | | 所示;当<i>k</i><0时,函数<i>f</i>(<i>x</i>)=<i>kx</i>+<i>b</i>在区间(-∞,+∞)上是减函数,如图3-13(2) 所示.</p> |
| | | <p class="center"><img class="img-b" alt="" src="../../assets/images/0098-5.jpg" /></p> |
| | | <p class="img">图3-13</p> |
| | | </div> |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" class="iframe-box"></iframe> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <img class="img-c" alt="" src="../../assets/images/0102-1.jpg" style="width: 40%" /> |
| | | </p> |
| | | <p class="img">图3-17</p> |
| | | <p v-if="isShowExampleTwo"> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 函数<i>f</i>(<i>x</i>)=|<i>x</i>|+1的定义域是(-∞,+∞),因为它是偶函数,所以根据其图像关于<i>y</i>轴对称的特点,即可画出这个函数在<i>x</i>∈(-∞,0]上的图像. |
| | | </p> |
| | | <p> |
| | | 如图3-18所示,在<i>y</i>轴右边的图像上取两点<i>A</i>和<i>B</i>,分别画出它们关于<i>y</i>轴对称的点<i>A</i>′和<i>B</i>′,然后连线<i>A</i>′<i>B</i>′,就得到这个函数的图像在<i>y</i>轴左边的部分. |
| | | </p> |
| | | <p class="center openImgBox"> |
| | | <img class="img-c" alt="" src="../../assets/images/0102-2.jpg" style="width: 40%" /> |
| | | </p> |
| | | <p class="img">图3-18</p> |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" class="iframe-box"></iframe> |
| | | <div v-if="isShowExampleTwo"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 函数<i>f</i>(<i>x</i>)=|<i>x</i>|+1的定义域是(-∞,+∞),因为它是偶函数,所以根据其图像关于<i>y</i>轴对称的特点,即可画出这个函数在<i>x</i>∈(-∞,0]上的图像. |
| | | </p> |
| | | <p> |
| | | 如图3-18所示,在<i>y</i>轴右边的图像上取两点<i>A</i>和<i>B</i>,分别画出它们关于<i>y</i>轴对称的点<i>A</i>′和<i>B</i>′,然后连线<i>A</i>′<i>B</i>′,就得到这个函数的图像在<i>y</i>轴左边的部分. |
| | | </p> |
| | | <p class="center openImgBox"> |
| | | <img class="img-c" alt="" src="../../assets/images/0102-2.jpg" style="width: 40%" /> |
| | | </p> |
| | | <p class="img">图3-18</p> |
| | | </div> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | <span class="btn-box" @click="openThinkingDialog"> |
| | | <span class="btn-box" @click="openDialog(thinkOne)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
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| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | <span class="btn-box" @click="stepDialog = true"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="15.28" height="17.563" viewBox="0 0 19.28 20.563"> |
| | | <g transform="translate(-109.056 -82.941)"> |
| | | <path class="a" |
| | | d="M3439.656-15185.7h-12.643a1.815,1.815,0,0,1-1.816-1.81v-16.944a1.83,1.83,0,0,1,1.816-1.809h15.674a1.8,1.8,0,0,1,1.79,1.809v13.93h-4.217a.6.6,0,0,0-.6.6v4.217h0Zm-9.819-2.764a.5.5,0,0,0-.5.5.5.5,0,0,0,.5.5h4a.5.5,0,0,0,.5-.5.5.5,0,0,0-.5-.5Zm0-2a.5.5,0,0,0-.5.5.5.5,0,0,0,.5.5h4a.5.5,0,0,0,.5-.5.5.5,0,0,0-.5-.5Zm1.393-8.525a2.416,2.416,0,0,0-2.416,2.411,2.421,2.421,0,0,0,2.416,2.42h.111a1.8,1.8,0,0,0,1.1,1.1,1.809,1.809,0,0,0,.6.107,1.808,1.808,0,0,0,1.7-1.206h4.072l-.172.172a.635.635,0,0,0-.179.454.569.569,0,0,0,.179.4.637.637,0,0,0,.435.176.6.6,0,0,0,.424-.176l1.2-1.214a.618.618,0,0,0,0-.858l-1.2-1.187a.619.619,0,0,0-.431-.176.6.6,0,0,0-.427.176.615.615,0,0,0,0,.854l.172.176h-4.072a1.8,1.8,0,0,0-1.1-1.1,1.755,1.755,0,0,0-.6-.1,1.808,1.808,0,0,0-1.7,1.206h-.111a.554.554,0,0,1-.145-.016,1.2,1.2,0,0,1-.84-.4,1.217,1.217,0,0,1-.3-.878,1.2,1.2,0,0,1,1.206-1.137.407.407,0,0,1,.069,0h3.729a1.807,1.807,0,0,0,1.118,1.114,1.816,1.816,0,0,0,.576.091,1.789,1.789,0,0,0,1.7-1.205h.309a2.415,2.415,0,0,0,1.679-.775,2.407,2.407,0,0,0,.637-1.729,2.411,2.411,0,0,0-2.419-2.324h-6.213a1.821,1.821,0,0,0-1.107-1.1,1.8,1.8,0,0,0-.6-.1,1.814,1.814,0,0,0-1.706,1.2,1.8,1.8,0,0,0,.077,1.389,1.787,1.787,0,0,0,1.026.92,1.841,1.841,0,0,0,.6.1,1.807,1.807,0,0,0,1.706-1.2h6.266a1.179,1.179,0,0,1,.836.4,1.22,1.22,0,0,1,.305.874,1.213,1.213,0,0,1-1.214,1.146h-.172a1.8,1.8,0,0,0-1.118-1.118,1.711,1.711,0,0,0-.576-.1,1.8,1.8,0,0,0-1.706,1.214Z" |
| | | transform="translate(-3316.14 15289.201)" /> |
| | | <path class="a" |
| | | d="M316.806,239.727a.6.6,0,1,0,.6-.6A.6.6,0,0,0,316.806,239.727Zm-5.421-4.207a.6.6,0,1,0,.6.6A.587.587,0,0,0,311.385,235.52Zm2.4,8.438a.607.607,0,1,0-.6-.613A.621.621,0,0,0,313.789,243.958Z" |
| | | transform="translate(-196.896 -148.921)" /> |
| | | <path class="a" d="M763.392,793.79l3.262-3.262h-3.262Z" transform="translate(-638.661 -690.634)" /> |
| | | </g> |
| | | </svg> |
| | | </span> |
| | | <span class="btn-box" @click="openMathDiaolog"> |
| | |
| | | <p>我们也可以由函数图像是否关于原点中心对称来判断函数是不是奇函数.</p> |
| | | <p class="center"><img class="img-f" alt="" src="../../assets/images/0105-1.jpg" /></p> |
| | | <p class="img">图3-20</p> |
| | | <p><span class="zt-ls"><b>例4</b></span> 根据图3-21中函数的图像,判断哪些函数是奇函数.</p> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例4</b></span> 根据图3-21中函数的图像,判断哪些函数是奇函数. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer24 = !isShowAnswer24"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="center"><img class="img-b" alt="" src="../../assets/images/0105-2.jpg" /></p> |
| | | <p class="img">图3-21</p> |
| | | <p><span class="zt-ls"><b>解</b></span> 在四个函数图像中,图3-21(1) 、图3-21(2) 和图3-21(3) 的函数图像关于原点中心对称;图3-21(4) |
| | | <p v-if="isShowAnswer24" ><span class="zt-ls"><b>解</b></span> 在四个函数图像中,图3-21(1) 、图3-21(2) 和图3-21(3) 的函数图像关于原点中心对称;图3-21(4) |
| | | 的函数图像不是关于原点中心对称的.根据奇函数的图像具有关于原点中心对称的特点,图3-21(1) 、图3-21(2) 和图3-21(3) 的函数是奇函数,图3-21(4) 的函数不是奇函数.</p> |
| | | </div> |
| | | </div> |
| | |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p><span class="zt-ls"><b>例5</b></span> 已知函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>图像在<i>y</i>轴右边的部分如图3-22所示.试画出这个函数图像在<i>y</i>轴左边的部分.</p> |
| | | <p><span class="zt-ls"><b>解</b></span> 函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>的定义域是(-∞,0)∪(0+∞),因为它是奇函数,所以根据其图像关于原点中心对称的特点,即可画出这个函数在<i>x</i>∈(-∞,0)上的图像.</p> |
| | | <p> |
| | | 如图3-23所示,在<i>y</i>轴右边的图像上取三个不同点<i>A</i>,<i>B</i>和<i>C</i>,并画出它们分别关于原点对称的点<i>A</i>′,<i>B</i>′和<i>C</i>′,然后按相同方式用光滑的曲线连线,就得到这个函数的图像在<i>y</i>轴左边的部分. |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例5</b></span> 已知函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>图像在<i>y</i>轴右边的部分如图3-22所示.试画出这个函数图像在<i>y</i>轴左边的部分. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer25 = !isShowAnswer25"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0106-3.jpg" /></p> |
| | | <p class="img">图3-22</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0106-4.jpg" /></p> |
| | | <p class="img">图3-23</p> |
| | | <p>与偶函数的判定方法类似,除了借助函数的图像来判断函数是不是奇函数,也可用定义判断函数是不是奇函数.</p> |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" class="iframe-box"></iframe> |
| | | <div v-if="isShowAnswer25" > |
| | | <p><span class="zt-ls"><b>解</b></span> 函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>的定义域是(-∞,0)∪(0+∞),因为它是奇函数,所以根据其图像关于原点中心对称的特点,即可画出这个函数在<i>x</i>∈(-∞,0)上的图像.</p> |
| | | <p> |
| | | 如图3-23所示,在<i>y</i>轴右边的图像上取三个不同点<i>A</i>,<i>B</i>和<i>C</i>,并画出它们分别关于原点对称的点<i>A</i>′,<i>B</i>′和<i>C</i>′,然后按相同方式用光滑的曲线连线,就得到这个函数的图像在<i>y</i>轴左边的部分. |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0106-4.jpg" /></p> |
| | | <p class="img">图3-23</p> |
| | | <p>与偶函数的判定方法类似,除了借助函数的图像来判断函数是不是奇函数,也可用定义判断函数是不是奇函数.</p> |
| | | </div> |
| | | <p><span class="zt-ls"><b>例6</b></span> 判断下列函数是不是奇函数.</p> |
| | | <p>(1) <i>f</i>(<i>x</i>)=<i>x</i><sup>3</sup>+<i>x</i>;(2) <math display="0"> |
| | | <p class="p-btn" > |
| | | <span>(1) <i>f</i>(<i>x</i>)=<i>x</i><sup>3</sup>+<i>x</i>;</span> |
| | | <span class="btn-box" @click="isShowAnswer26 = !isShowAnswer26"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer26" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) |
| | | 函数<i>f</i>(<i>x</i>)=<i>x</i><sup>3</sup>+<i>x</i>的定义域是<b>R</b>,对任意<i>x</i>∈<b>R</b>,都有-<i>x</i>∈<b>R</b>,且 |
| | | </p> |
| | | <p class="center"> |
| | | <i>f</i>(-<i>x</i>)=(-<i>x</i>)<sup>3</sup>+(-<i>x</i>)=-<i>x</i><sup>3</sup>-<i>x</i>=-(<i>x</i><sup>3</sup>+<i>x</i>)=-<i>f</i>(<i>x</i>). |
| | | </p> |
| | | <p>所以,函数<i>f</i>(<i>x</i>)=<i>x</i><sup>3</sup>+<i>x</i>是奇函数.</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span> |
| | | (2) <math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>; |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer27 = !isShowAnswer27"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer27" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(2) |
| | | 要使函数<i>f</i>(<i>x</i>)有意义,必须满足<i>x</i>≠0,所以函数<i>f</i>(<i>x</i>)的定义域是<i>D</i>={<i>x</i>|<i>x</i>≠0},对任意<i>x</i>∈<i>D</i>,都有-<i>x</i>∈<i>D</i>,且 |
| | | </p> |
| | | <math display="block"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>;(3) <i>f</i>(<i>x</i>)=<i>x</i>+|<i>x</i>|.</p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) |
| | | 函数<i>f</i>(<i>x</i>)=<i>x</i><sup>3</sup>+<i>x</i>的定义域是<b>R</b>,对任意<i>x</i>∈<b>R</b>,都有-<i>x</i>∈<b>R</b>,且 |
| | | </p> |
| | | <p class="center"> |
| | | <i>f</i>(-<i>x</i>)=(-<i>x</i>)<sup>3</sup>+(-<i>x</i>)=-<i>x</i><sup>3</sup>-<i>x</i>=-(<i>x</i><sup>3</sup>+<i>x</i>)=-<i>f</i>(<i>x</i>). |
| | | </p> |
| | | <p>所以,函数<i>f</i>(<i>x</i>)=<i>x</i><sup>3</sup>+<i>x</i>是奇函数.</p> |
| | | <p>(2) |
| | | 要使函数<i>f</i>(<i>x</i>)有意义,必须满足<i>x</i>≠0,所以函数<i>f</i>(<i>x</i>)的定义域是<i>D</i>={<i>x</i>|<i>x</i>≠0},对任意<i>x</i>∈<i>D</i>,都有-<i>x</i>∈<i>D</i>,且 |
| | | </p> |
| | | <math display="block"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p>所以,函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>是奇函数.</p> |
| | | <p>(3) 函数<i>f</i>(<i>x</i>)=<i>x</i>+|<i>x</i>|的定义域是<b>R</b>,对任意<i>x</i>∈<b>R</b>,都有-<i>x</i>∈<b>R</b>,但是</p> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p>所以,函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>是奇函数. |
| | | </p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(3) <i>f</i>(<i>x</i>)=<i>x</i>+|<i>x</i>|.</span> |
| | | <span class="btn-box" @click="isShowAnswer28 = !isShowAnswer28"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer28" > |
| | | <p > <span class="zt-ls"><b>解</b></span>(3) 函数<i>f</i>(<i>x</i>)=<i>x</i>+|<i>x</i>|的定义域是<b>R</b>,对任意<i>x</i>∈<b>R</b>,都有-<i>x</i>∈<b>R</b>,但是</p> |
| | | <p class="center"> |
| | | <i>f</i>(-<i>x</i>)=(-<i>x</i>)+|-<i>x</i>|=-<i>x</i>+|<i>x</i>|=-(<i>x</i>-|<i>x</i>|)≠-<i>f</i>(<i>x</i>). |
| | | </p> |
| | | <p>所以,函数<i>f</i>(<i>x</i>)=<i>x</i>+|<i>x</i>|不是奇函数.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p class="center"> |
| | | <i>f</i>(-<i>x</i>)=(-<i>x</i>)+|-<i>x</i>|=-<i>x</i>+|<i>x</i>|=-(<i>x</i>-|<i>x</i>|)≠-<i>f</i>(<i>x</i>). |
| | | </p> |
| | | <p>所以,函数<i>f</i>(<i>x</i>)=<i>x</i>+|<i>x</i>|不是奇函数.</p> |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"> |
| | |
| | | </div> |
| | | <p>如果一个函数是奇函数或偶函数,那么就称这个函数具有<b>奇偶性</b>.否则,函数不具有奇偶性.</p> |
| | | <p><span class="zt-ls"><b>例7</b></span> 判断下列函数的奇偶性.</p> |
| | | <p>(1) <i>f</i>(<i>x</i>)=<i>x</i><sup>4</sup>;(2) <math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>;</p> |
| | | <p>(3) <i>f</i>(<i>x</i>)=<i>x</i><sup>2</sup>+<i>x</i>;(4)<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>.</p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) |
| | | <i>f</i>(<i>x</i>)的定义域是<b>R</b>,对任意<i>x</i>∈<b>R</b>,都有-<i>x</i>∈<b>R</b>,且 |
| | | <p class="p-btn" > |
| | | <span>(1) <i>f</i>(<i>x</i>)=<i>x</i><sup>4</sup>;</span> |
| | | <span class="btn-box" @click="isShowAnswer29 = !isShowAnswer29"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="center"><i>f</i>(-<i>x</i>)=(-<i>x</i>)<sup>4</sup>=<i>x</i><sup>4</sup>=<i>f</i>(<i>x</i>),</p> |
| | | <p>所以,函数<i>f</i>(<i>x</i>)=<i>x</i><sup>4</sup>是偶函数.</p> |
| | | <p>(2) |
| | | 要使函数<i>f</i>(<i>x</i>)有意义,必须满足<i>x</i>≠0,所以函数<i>f</i>(<i>x</i>)的定义域是<i>D</i>={<i>x</i>|<i>x</i>≠0},对任意<i>x</i>∈<i>D</i>,都有-<i>x</i>∈<i>D</i>, |
| | | 且</p> |
| | | <math display="block"> |
| | | <mi>f</mi> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <div v-if="isShowAnswer29" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) |
| | | <i>f</i>(<i>x</i>)的定义域是<b>R</b>,对任意<i>x</i>∈<b>R</b>,都有-<i>x</i>∈<b>R</b>,且 |
| | | </p> |
| | | <p class="center"><i>f</i>(-<i>x</i>)=(-<i>x</i>)<sup>4</sup>=<i>x</i><sup>4</sup>=<i>f</i>(<i>x</i>),</p> |
| | | <p>所以,函数<i>f</i>(<i>x</i>)=<i>x</i><sup>4</sup>是偶函数.</p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | <span> |
| | | (2) <math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>; |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer30 = !isShowAnswer30"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer30" > |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(2) |
| | | 要使函数<i>f</i>(<i>x</i>)有意义,必须满足<i>x</i>≠0,所以函数<i>f</i>(<i>x</i>)的定义域是<i>D</i>={<i>x</i>|<i>x</i>≠0},对任意<i>x</i>∈<i>D</i>,都有-<i>x</i>∈<i>D</i>, |
| | | 且</p> |
| | | <math display="block"> |
| | | <mi>f</mi> |
| | | <mo stretchy="false">(</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>f</mi> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>x</mi> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>,</mo> |
| | | </math> |
| | | <p>所以,函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>是奇函数.</p> |
| | | <p>(3) |
| | | 函数<i>f</i>(<i>x</i>)=<i>x</i><sup>2</sup>+<i>x</i>的定义域是<b>R</b>,对任意<i>x</i>∈<b>R</b>,都有-<i>x</i>∈<b>R</b>,且 |
| | | </p> |
| | | <p class="center"><i>f</i>(-<i>x</i>)=(-<i>x</i>)<sup>2</sup>+(-<i>x</i>)=<i>x</i><sup>2</sup>-<i>x</i>,</p> |
| | | <p>但 <i>f</i>(-<i>x</i>)≠<i>f</i>(<i>x</i>),且<i>f</i>(-<i>x</i>)≠-<i>f</i>(<i>x</i>),</p> |
| | | <p>所以,函数<i>f</i>(<i>x</i>)=<i>x</i><sup>2</sup>+<i>x</i>既不是奇函数,也不是偶函数.</p> |
| | | <p>(4) |
| | | 要使函数<i>f</i>(<i>x</i>)有意义,必须满足<i>x</i>-1≠0,所以函数<i>f</i>(<i>x</i>)的定义域是<i>D</i>={<i>x</i>|<i>x</i>≠1},对任意<i>x</i>∈<i>D</i>,不都有-<i>x</i>∈<i>D</i>成立. |
| | | </p> |
| | | <p>所以,函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>不具有奇偶性,它既不是奇函数也不是偶函数.</p> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mi>f</mi> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>x</mi> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>,</mo> |
| | | </math> |
| | | <p>所以,函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>x</mi> |
| | | </mfrac> |
| | | </math>是奇函数. |
| | | </p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | <span> |
| | | (3) <i>f</i>(<i>x</i>)=<i>x</i><sup>2</sup>+<i>x</i>; |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer31 = !isShowAnswer31"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer31" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(3) |
| | | 函数<i>f</i>(<i>x</i>)=<i>x</i><sup>2</sup>+<i>x</i>的定义域是<b>R</b>,对任意<i>x</i>∈<b>R</b>,都有-<i>x</i>∈<b>R</b>,且 |
| | | </p> |
| | | <p class="center"><i>f</i>(-<i>x</i>)=(-<i>x</i>)<sup>2</sup>+(-<i>x</i>)=<i>x</i><sup>2</sup>-<i>x</i>,</p> |
| | | <p>但 <i>f</i>(-<i>x</i>)≠<i>f</i>(<i>x</i>),且<i>f</i>(-<i>x</i>)≠-<i>f</i>(<i>x</i>),</p> |
| | | <p>所以,函数<i>f</i>(<i>x</i>)=<i>x</i><sup>2</sup>+<i>x</i>既不是奇函数,也不是偶函数.</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span> |
| | | (4)<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>. |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer32 = !isShowAnswer32"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer32" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(4) |
| | | 要使函数<i>f</i>(<i>x</i>)有意义,必须满足<i>x</i>-1≠0,所以函数<i>f</i>(<i>x</i>)的定义域是<i>D</i>={<i>x</i>|<i>x</i>≠1},对任意<i>x</i>∈<i>D</i>,不都有-<i>x</i>∈<i>D</i>成立. |
| | | </p> |
| | | <p>所以,函数<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>不具有奇偶性,它既不是奇函数也不是偶函数. |
| | | </p> |
| | | </div> |
| | | <div class="bk-hzjl"> |
| | | <div class="bj1-hzjl"> |
| | | <p class="left"><img class="img-gn2" alt="" src="../../assets/images/hzjl.jpg" /></p> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p><span class="zt-ls"><b>例1</b></span> 住在A城的小李早晨8:00出发,驾驶小轿车从A城以80 km/h 的速度到200 km处的B城,他在B城停留了3 h 后,再以100 |
| | | km/h的速度返回A城.在不考虑堵车等其他因素的情况下,设小李从A城出发<i>x</i>(h)后,小李与A城的距离是<i>y</i>(km).</p> |
| | | <p>(1) 用解析法表示函数<i>y</i>=<i>f</i>(<i>x</i>);</p> |
| | | <p>(2) 画出函数<i>y</i>=<i>f</i>(<i>x</i>)的图像;</p> |
| | | <p>(3) 小李在返回A城途中,15:00刚好接到家人的电话,这时他距离A城多少千米?</p> |
| | | <p class="block"><span |
| | | class="zt-ls2"><b>分析</b></span> 首先求出小李从A城到B城和从B城返回A城共花费的时间,明确函数的定义域.小李去B城和返回A城的过程中,<i>y</i>与<i>x</i>分别对应的解析式不相同,所以该函数需用分段函数表示. |
| | | <p> |
| | | <span> |
| | | <span class="zt-ls"> |
| | | <b>例1</b></span> 住在A城的小李早晨8:00出发,驾驶小轿车从A城以80 km/h 的速度到200 km处的B城,他在B城停留了3 h 后,再以100 |
| | | km/h的速度返回A城.在不考虑堵车等其他因素的情况下,设小李从A城出发<i>x</i>(h)后,小李与A城的距离是<i>y</i>(km). |
| | | </span> |
| | | <span class="btn-box" @click="openDialog(thinkFive)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
| | | d="M3771.2-14311.889a2.356,2.356,0,0,1-1.727-.626c-.027-.054-.053-.1-.079-.148l0-.007c-.123-.224-.2-.371-.076-.629a.869.869,0,0,1,.784-.471.205.205,0,0,1,.158.079.205.205,0,0,0,.158.079.187.187,0,0,0,.038.1.143.143,0,0,0,.117.05h.158a.573.573,0,0,0,.471.158,2.2,2.2,0,0,0,.916-.3l.023-.011a.572.572,0,0,1,.471-.158.575.575,0,0,1,.626.626.526.526,0,0,1,.036.409.664.664,0,0,1-.349.375A3.582,3.582,0,0,1,3771.2-14311.889Zm-1.885-1.723h-.155a.718.718,0,0,1-.784-.63.38.38,0,0,1-.021-.3.976.976,0,0,1,.492-.485l4.86-1.252a1.047,1.047,0,0,1,.784.626c.151.3-.128.61-.471.784l-4.705,1.256Zm-.155-1.885H3769a.716.716,0,0,1-.784-.626c-.149-.3.129-.611.471-.784l4.234-1.1v-.158l-.021.007a7.808,7.808,0,0,1-1.861.31,5.3,5.3,0,0,1-3.137-.942,5.789,5.789,0,0,1-2.666-4.076,6.421,6.421,0,0,1,1.256-5.018,7.038,7.038,0,0,1,2.194-1.568,7.848,7.848,0,0,1,2.666-.472,6.43,6.43,0,0,1,2.979.784,4.958,4.958,0,0,1,2.2,2.194,5.522,5.522,0,0,1,.313,5.177,13.113,13.113,0,0,1-1.256,1.882l-.313.313a2.156,2.156,0,0,0-.78,1.244l0,.012a1.731,1.731,0,0,1-1.727,1.723l-.313.158-3.292.939Zm1.256-6.271v1.256h1.41v-1.256Zm.784-4.234c.718,0,1.1.271,1.1.784a.925.925,0,0,1-.316.783l-.468.156a2.235,2.235,0,0,0-.63.471l-.012.024a2.2,2.2,0,0,0-.3.918v.155h1.1v-.155a1.2,1.2,0,0,1,.313-.629.543.543,0,0,0,.315-.153c.007,0,.315,0,.315-.16a1.226,1.226,0,0,0,.626-.626,2.277,2.277,0,0,0,.313-1.1,1.409,1.409,0,0,0-.626-1.252,2.337,2.337,0,0,0-1.569-.471,2.258,2.258,0,0,0-2.507,2.353l1.252.154A1.121,1.121,0,0,1,3771.2-14326Zm-6.51,9.645a.769.769,0,0,1-.549-.237.772.772,0,0,1-.235-.549.772.772,0,0,1,.235-.548l.939-.939a.781.781,0,0,1,.55-.234.772.772,0,0,1,.547.234.772.772,0,0,1,.238.549.772.772,0,0,1-.238.549l-.939.938A.769.769,0,0,1,3764.686-14316.356Zm13.174-.157a.774.774,0,0,1-.549-.234l-.943-.942a.678.678,0,0,1-.233-.47.678.678,0,0,1,.233-.47.774.774,0,0,1,.549-.234.774.774,0,0,1,.549.234l.942.939a.427.427,0,0,1,.228.324.74.74,0,0,1-.228.618A.774.774,0,0,1,3777.859-14316.514Zm2.9-6.351h-1.414c-.469-.158-.784-.474-.784-.784a.743.743,0,0,1,.784-.784h1.414a.743.743,0,0,1,.784.784A.743.743,0,0,1,3780.761-14322.864Zm-17.566-.158h-1.41c-.469-.157-.784-.473-.784-.784a.743.743,0,0,1,.784-.784h1.41a.743.743,0,0,1,.784.784A.743.743,0,0,1,3763.195-14323.022Zm13.861-5.723a.759.759,0,0,1-.529-.237.776.776,0,0,1-.235-.549.772.772,0,0,1,.235-.549l.939-.938a.44.44,0,0,1,.413-.238.759.759,0,0,1,.529.238.772.772,0,0,1,.235.549.772.772,0,0,1-.235.548l-.942.939A.435.435,0,0,1,3777.055-14328.745Zm-11.429,0a.776.776,0,0,1-.55-.237l-.939-1.1a.678.678,0,0,1-.235-.469.678.678,0,0,1,.235-.47.772.772,0,0,1,.549-.238.772.772,0,0,1,.549.238l.939,1.1a.675.675,0,0,1,.238.47.675.675,0,0,1-.238.47A.767.767,0,0,1,3765.626-14328.745Zm5.724-2.273a.743.743,0,0,1-.784-.785v-1.413c.157-.469.473-.784.784-.784a.743.743,0,0,1,.784.784v1.413A.743.743,0,0,1,3771.35-14331.019Z" |
| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 小李从A城出发到B 城用时<math display="0"> |
| | | <mfrac> |
| | | <mn>200</mn> |
| | | <mn>80</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>2.5</mn> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>h</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,<i>x</i>的取值范围是{<i>x</i>|0<<i>x</i>≤2.5},<i>y</i>与<i>x</i>的对应关系是<i>y</i>=80<i>x</i>;</p> |
| | | <p>小李到B城后停留3 h,x的取值范围是{<i>x</i>|2.5<<i>x</i>≤5.5},对应关系是<i>y</i>=200;</p> |
| | | <p>小李从<i>B</i>城返回<i>A</i>城用时<math display="0"> |
| | | <mfrac> |
| | | <mn>200</mn> |
| | | <mn>100</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>h</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,<i>x</i>的取值范围是{<i>x</i>|5.5<<i>x</i>≤7.5},<i>y</i>与<i>x</i>的对应关系是<i>y</i>=200-100(<i>x</i>-5.5),即<i>y</i>=-100<i>x</i>+750. |
| | | <p class="p-btn" > |
| | | <span> |
| | | (1) 用解析法表示函数<i>y</i>=<i>f</i>(<i>x</i>); |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer33 = !isShowAnswer33"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p>因此,用解析法将函数<i>f</i>(<i>x</i>)表示为<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnalign="left left" columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>80</mn> |
| | | <mi>x</mi> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd> |
| | | <mn>0</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>⩽</mo> |
| | | <mn>2.5</mn> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>200</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd> |
| | | <mn>2.5</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>⩽</mo> |
| | | <mn>5.5</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>−</mo> |
| | | <mn>100</mn> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>750</mn> |
| | | <mo>,</mo> |
| | | <mn>5.5</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>⩽</mo> |
| | | <mn>7.5</mn> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>.</p> |
| | | <p>(2) 函数<i>y</i>=<i>f</i>(<i>x</i>)的图像如图3-24所示.</p> |
| | | <p class="center"><img class="img-f" alt="" src="../../assets/images/0111-4.jpg" /></p> |
| | | <p class="img">图3-24</p> |
| | | <p>(3) 小李从早晨8:00出发到15:00,共经过了7h,所以<i>x</i>=7,由(1) 中解析式得小李与<i>A</i>城的距离为</p> |
| | | <p class="center">-100×7+750=50(km).</p> |
| | | <p>所以,小李返回A城途中接到家人电话时,距离A城刚好50 km.</p> |
| | | <div v-if="isShowAnswer33" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 小李从A城出发到B 城用时<math display="0"> |
| | | <mfrac> |
| | | <mn>200</mn> |
| | | <mn>80</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>2.5</mn> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>h</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,<i>x</i>的取值范围是{<i>x</i>|0<<i>x</i>≤2.5},<i>y</i>与<i>x</i>的对应关系是<i>y</i>=80<i>x</i>;</p> |
| | | <p>小李到B城后停留3 h,x的取值范围是{<i>x</i>|2.5<<i>x</i>≤5.5},对应关系是<i>y</i>=200;</p> |
| | | <p>小李从<i>B</i>城返回<i>A</i>城用时<math display="0"> |
| | | <mfrac> |
| | | <mn>200</mn> |
| | | <mn>100</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>h</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,<i>x</i>的取值范围是{<i>x</i>|5.5<<i>x</i>≤7.5},<i>y</i>与<i>x</i>的对应关系是<i>y</i>=200-100(<i>x</i>-5.5),即<i>y</i>=-100<i>x</i>+750. |
| | | </p> |
| | | <p>因此,用解析法将函数<i>f</i>(<i>x</i>)表示为<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnalign="left left" columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>80</mn> |
| | | <mi>x</mi> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd> |
| | | <mn>0</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>⩽</mo> |
| | | <mn>2.5</mn> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>200</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd> |
| | | <mn>2.5</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>⩽</mo> |
| | | <mn>5.5</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>−</mo> |
| | | <mn>100</mn> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>750</mn> |
| | | <mo>,</mo> |
| | | <mn>5.5</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>⩽</mo> |
| | | <mn>7.5</mn> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>. |
| | | </p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span>(2) 画出函数<i>y</i>=<i>f</i>(<i>x</i>)的图像;</span> |
| | | <span class="btn-box" @click="isShowAnswer34 = !isShowAnswer34"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer34"> |
| | | <p> <span class="zt-ls"><b>解</b></span>(2) 函数<i>y</i>=<i>f</i>(<i>x</i>)的图像如图3-24所示.</p> |
| | | <p class="center"><img class="img-f" alt="" src="../../assets/images/0111-4.jpg" /></p> |
| | | <p class="img">图3-24</p> |
| | | </div> |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" class="iframe-box"></iframe> |
| | | <p class="p-btn" > |
| | | <span>(3) 小李在返回A城途中,15:00刚好接到家人的电话,这时他距离A城多少千米?</span> |
| | | <span class="btn-box" @click="isShowAnswer35 = !isShowAnswer35"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer35" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(3) 小李从早晨8:00出发到15:00,共经过了7h,所以<i>x</i>=7,由(1) 中解析式得小李与<i>A</i>城的距离为</p> |
| | | <p class="center">-100×7+750=50(km).</p> |
| | | <p>所以,小李返回A城途中接到家人电话时,距离A城刚好50 km.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p><span class="zt-ls"><b>例2</b></span> 某农户要用6 000块砖建造三间面积相等的饲养室,如图3-25所示,其中<i>AB</i>,<i>AD</i>两面靠墙,每修筑长度1 |
| | | m的新墙需要砖200块.当<i>AB</i>为多少米时,修建的三间饲养室的总面积最大?最大面积是多少?</p> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例2</b></span> 某农户要用6 000块砖建造三间面积相等的饲养室,如图3-25所示,其中<i>AB</i>,<i>AD</i>两面靠墙,每修筑长度1 |
| | | m的新墙需要砖200块.当<i>AB</i>为多少米时,修建的三间饲养室的总面积最大?最大面积是多少? |
| | | </span> |
| | | <span class="btn-box" @click="openDialog(thinkSix)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
| | | d="M3771.2-14311.889a2.356,2.356,0,0,1-1.727-.626c-.027-.054-.053-.1-.079-.148l0-.007c-.123-.224-.2-.371-.076-.629a.869.869,0,0,1,.784-.471.205.205,0,0,1,.158.079.205.205,0,0,0,.158.079.187.187,0,0,0,.038.1.143.143,0,0,0,.117.05h.158a.573.573,0,0,0,.471.158,2.2,2.2,0,0,0,.916-.3l.023-.011a.572.572,0,0,1,.471-.158.575.575,0,0,1,.626.626.526.526,0,0,1,.036.409.664.664,0,0,1-.349.375A3.582,3.582,0,0,1,3771.2-14311.889Zm-1.885-1.723h-.155a.718.718,0,0,1-.784-.63.38.38,0,0,1-.021-.3.976.976,0,0,1,.492-.485l4.86-1.252a1.047,1.047,0,0,1,.784.626c.151.3-.128.61-.471.784l-4.705,1.256Zm-.155-1.885H3769a.716.716,0,0,1-.784-.626c-.149-.3.129-.611.471-.784l4.234-1.1v-.158l-.021.007a7.808,7.808,0,0,1-1.861.31,5.3,5.3,0,0,1-3.137-.942,5.789,5.789,0,0,1-2.666-4.076,6.421,6.421,0,0,1,1.256-5.018,7.038,7.038,0,0,1,2.194-1.568,7.848,7.848,0,0,1,2.666-.472,6.43,6.43,0,0,1,2.979.784,4.958,4.958,0,0,1,2.2,2.194,5.522,5.522,0,0,1,.313,5.177,13.113,13.113,0,0,1-1.256,1.882l-.313.313a2.156,2.156,0,0,0-.78,1.244l0,.012a1.731,1.731,0,0,1-1.727,1.723l-.313.158-3.292.939Zm1.256-6.271v1.256h1.41v-1.256Zm.784-4.234c.718,0,1.1.271,1.1.784a.925.925,0,0,1-.316.783l-.468.156a2.235,2.235,0,0,0-.63.471l-.012.024a2.2,2.2,0,0,0-.3.918v.155h1.1v-.155a1.2,1.2,0,0,1,.313-.629.543.543,0,0,0,.315-.153c.007,0,.315,0,.315-.16a1.226,1.226,0,0,0,.626-.626,2.277,2.277,0,0,0,.313-1.1,1.409,1.409,0,0,0-.626-1.252,2.337,2.337,0,0,0-1.569-.471,2.258,2.258,0,0,0-2.507,2.353l1.252.154A1.121,1.121,0,0,1,3771.2-14326Zm-6.51,9.645a.769.769,0,0,1-.549-.237.772.772,0,0,1-.235-.549.772.772,0,0,1,.235-.548l.939-.939a.781.781,0,0,1,.55-.234.772.772,0,0,1,.547.234.772.772,0,0,1,.238.549.772.772,0,0,1-.238.549l-.939.938A.769.769,0,0,1,3764.686-14316.356Zm13.174-.157a.774.774,0,0,1-.549-.234l-.943-.942a.678.678,0,0,1-.233-.47.678.678,0,0,1,.233-.47.774.774,0,0,1,.549-.234.774.774,0,0,1,.549.234l.942.939a.427.427,0,0,1,.228.324.74.74,0,0,1-.228.618A.774.774,0,0,1,3777.859-14316.514Zm2.9-6.351h-1.414c-.469-.158-.784-.474-.784-.784a.743.743,0,0,1,.784-.784h1.414a.743.743,0,0,1,.784.784A.743.743,0,0,1,3780.761-14322.864Zm-17.566-.158h-1.41c-.469-.157-.784-.473-.784-.784a.743.743,0,0,1,.784-.784h1.41a.743.743,0,0,1,.784.784A.743.743,0,0,1,3763.195-14323.022Zm13.861-5.723a.759.759,0,0,1-.529-.237.776.776,0,0,1-.235-.549.772.772,0,0,1,.235-.549l.939-.938a.44.44,0,0,1,.413-.238.759.759,0,0,1,.529.238.772.772,0,0,1,.235.549.772.772,0,0,1-.235.548l-.942.939A.435.435,0,0,1,3777.055-14328.745Zm-11.429,0a.776.776,0,0,1-.55-.237l-.939-1.1a.678.678,0,0,1-.235-.469.678.678,0,0,1,.235-.47.772.772,0,0,1,.549-.238.772.772,0,0,1,.549.238l.939,1.1a.675.675,0,0,1,.238.47.675.675,0,0,1-.238.47A.767.767,0,0,1,3765.626-14328.745Zm5.724-2.273a.743.743,0,0,1-.784-.785v-1.413c.157-.469.473-.784.784-.784a.743.743,0,0,1,.784.784v1.413A.743.743,0,0,1,3771.35-14331.019Z" |
| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer36 = !isShowAnswer36"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p class="center"><img class="img-f" alt="" src="../../assets/images/0112-1.jpg" /></p> |
| | | <p class="img">图3-25</p> |
| | | <p class="block"><span |
| | | class="zt-ls2"><b>分析</b></span> 首先需要计算备用材料可修建饲养室新墙的总长;因每间饲养室的周长是定值,所以设<i>AB</i>的长为<i>x</i>(m),就可以用含<i>x</i>的代数式表示<i>BC</i>的长;再用解析法表示总面积<i>y</i>(m<sup>2</sup>)与<i>x</i>(m)的函数关系;然后利用函数的性质来解决问题. |
| | | <div v-if="isShowAnswer36" > |
| | | <p><span class="zt-ls"><b>解</b></span> 因为每修筑长度1 m的新墙需要砖200块,所以6 000块砖可以修筑新墙的总长度是6 |
| | | 000÷200=30(m).设<i>AB</i>为<i>x</i>(m),则<i>BC</i>为(30-3<i>x</i>)(m),三间饲养室的总面积为<i>y</i>(m<sup>2</sup>).</p> |
| | | <p>于是<i>y</i>=(30-3<i>x</i>)<i>x</i>,要有实际意义,必须满足<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>30</mn> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>.</p> |
| | | <p>所以,<i>y</i>与<i>x</i>的函数关系是<i>y</i>=-3<i>x</i><sup>2</sup>+30<i>x</i>,0<<i>x</i><10.</p> |
| | | <p>整理得<i>y</i>=-3(<i>x</i>-5)<sup>2</sup>+75.</p> |
| | | <p>所以,当<i>x</i>=5时,<i>y</i>值最大,最大值为75.</p> |
| | | <p>即当<i>AB</i>为5 m时,三间饲养室的总面积最大,最大面积是75 m<sup>2</sup>.</p> |
| | | <p>在实际生活中,很多与二次函数有关的最值问题都可通过分析、研究后,建立相应二次函数的数学模型,并运用二次函数的图像性质求最值.</p> |
| | | </div> |
| | | <p class="p-btn" > |
| | | <span> |
| | | <span class="zt-ls"><b>例3</b></span> 某批发商购入一批30元/kg的绿色食品,若以40元/kg销售,则每月可批发销售400 |
| | | kg.由批发销售经验知道,每月销售量<i>y</i>(kg |
| | | )是销售单价<i>x</i>(元)的一次函数,其图像如图3-26所示. |
| | | </span> |
| | | <span class="btn-box" @click="openDialog(thinkSeven)"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.545" height="18.112" viewBox="0 0 20.545 22.112"> |
| | | <path class="a" |
| | | d="M3771.2-14311.889a2.356,2.356,0,0,1-1.727-.626c-.027-.054-.053-.1-.079-.148l0-.007c-.123-.224-.2-.371-.076-.629a.869.869,0,0,1,.784-.471.205.205,0,0,1,.158.079.205.205,0,0,0,.158.079.187.187,0,0,0,.038.1.143.143,0,0,0,.117.05h.158a.573.573,0,0,0,.471.158,2.2,2.2,0,0,0,.916-.3l.023-.011a.572.572,0,0,1,.471-.158.575.575,0,0,1,.626.626.526.526,0,0,1,.036.409.664.664,0,0,1-.349.375A3.582,3.582,0,0,1,3771.2-14311.889Zm-1.885-1.723h-.155a.718.718,0,0,1-.784-.63.38.38,0,0,1-.021-.3.976.976,0,0,1,.492-.485l4.86-1.252a1.047,1.047,0,0,1,.784.626c.151.3-.128.61-.471.784l-4.705,1.256Zm-.155-1.885H3769a.716.716,0,0,1-.784-.626c-.149-.3.129-.611.471-.784l4.234-1.1v-.158l-.021.007a7.808,7.808,0,0,1-1.861.31,5.3,5.3,0,0,1-3.137-.942,5.789,5.789,0,0,1-2.666-4.076,6.421,6.421,0,0,1,1.256-5.018,7.038,7.038,0,0,1,2.194-1.568,7.848,7.848,0,0,1,2.666-.472,6.43,6.43,0,0,1,2.979.784,4.958,4.958,0,0,1,2.2,2.194,5.522,5.522,0,0,1,.313,5.177,13.113,13.113,0,0,1-1.256,1.882l-.313.313a2.156,2.156,0,0,0-.78,1.244l0,.012a1.731,1.731,0,0,1-1.727,1.723l-.313.158-3.292.939Zm1.256-6.271v1.256h1.41v-1.256Zm.784-4.234c.718,0,1.1.271,1.1.784a.925.925,0,0,1-.316.783l-.468.156a2.235,2.235,0,0,0-.63.471l-.012.024a2.2,2.2,0,0,0-.3.918v.155h1.1v-.155a1.2,1.2,0,0,1,.313-.629.543.543,0,0,0,.315-.153c.007,0,.315,0,.315-.16a1.226,1.226,0,0,0,.626-.626,2.277,2.277,0,0,0,.313-1.1,1.409,1.409,0,0,0-.626-1.252,2.337,2.337,0,0,0-1.569-.471,2.258,2.258,0,0,0-2.507,2.353l1.252.154A1.121,1.121,0,0,1,3771.2-14326Zm-6.51,9.645a.769.769,0,0,1-.549-.237.772.772,0,0,1-.235-.549.772.772,0,0,1,.235-.548l.939-.939a.781.781,0,0,1,.55-.234.772.772,0,0,1,.547.234.772.772,0,0,1,.238.549.772.772,0,0,1-.238.549l-.939.938A.769.769,0,0,1,3764.686-14316.356Zm13.174-.157a.774.774,0,0,1-.549-.234l-.943-.942a.678.678,0,0,1-.233-.47.678.678,0,0,1,.233-.47.774.774,0,0,1,.549-.234.774.774,0,0,1,.549.234l.942.939a.427.427,0,0,1,.228.324.74.74,0,0,1-.228.618A.774.774,0,0,1,3777.859-14316.514Zm2.9-6.351h-1.414c-.469-.158-.784-.474-.784-.784a.743.743,0,0,1,.784-.784h1.414a.743.743,0,0,1,.784.784A.743.743,0,0,1,3780.761-14322.864Zm-17.566-.158h-1.41c-.469-.157-.784-.473-.784-.784a.743.743,0,0,1,.784-.784h1.41a.743.743,0,0,1,.784.784A.743.743,0,0,1,3763.195-14323.022Zm13.861-5.723a.759.759,0,0,1-.529-.237.776.776,0,0,1-.235-.549.772.772,0,0,1,.235-.549l.939-.938a.44.44,0,0,1,.413-.238.759.759,0,0,1,.529.238.772.772,0,0,1,.235.549.772.772,0,0,1-.235.548l-.942.939A.435.435,0,0,1,3777.055-14328.745Zm-11.429,0a.776.776,0,0,1-.55-.237l-.939-1.1a.678.678,0,0,1-.235-.469.678.678,0,0,1,.235-.47.772.772,0,0,1,.549-.238.772.772,0,0,1,.549.238l.939,1.1a.675.675,0,0,1,.238.47.675.675,0,0,1-.238.47A.767.767,0,0,1,3765.626-14328.745Zm5.724-2.273a.743.743,0,0,1-.784-.785v-1.413c.157-.469.473-.784.784-.784a.743.743,0,0,1,.784.784v1.413A.743.743,0,0,1,3771.35-14331.019Z" |
| | | transform="translate(-3761 14334.001)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <p><span class="zt-ls"><b>解</b></span> 因为每修筑长度1 m的新墙需要砖200块,所以6 000块砖可以修筑新墙的总长度是6 |
| | | 000÷200=30(m).设<i>AB</i>为<i>x</i>(m),则<i>BC</i>为(30-3<i>x</i>)(m),三间饲养室的总面积为<i>y</i>(m<sup>2</sup>).</p> |
| | | <p>于是<i>y</i>=(30-3<i>x</i>)<i>x</i>,要有实际意义,必须满足<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>30</mn> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>.</p> |
| | | <p>所以,<i>y</i>与<i>x</i>的函数关系是<i>y</i>=-3<i>x</i><sup>2</sup>+30<i>x</i>,0<<i>x</i><10.</p> |
| | | <p>整理得<i>y</i>=-3(<i>x</i>-5)<sup>2</sup>+75.</p> |
| | | <p>所以,当<i>x</i>=5时,<i>y</i>值最大,最大值为75.</p> |
| | | <p>即当<i>AB</i>为5 m时,三间饲养室的总面积最大,最大面积是75 m<sup>2</sup>.</p> |
| | | <p>在实际生活中,很多与二次函数有关的最值问题都可通过分析、研究后,建立相应二次函数的数学模型,并运用二次函数的图像性质求最值.</p> |
| | | <p><span class="zt-ls"><b>例3</b></span> 某批发商购入一批30元/kg的绿色食品,若以40元/kg销售,则每月可批发销售400 |
| | | kg.由批发销售经验知道,每月销售量<i>y</i>(kg |
| | | )是销售单价<i>x</i>(元)的一次函数,其图像如图3-26所示.</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0112-3.jpg" /></p> |
| | | <p class="img"> 图3-26</p> |
| | | <p>(1) 用解析法表示函数<i>y</i>=<i>f</i>(<i>x</i>);</p> |
| | | <p>(2) 该批发商不低于购入价进行销售,设该批发商每月销售这批绿色食品可获得利润为<i>w</i>元,用解析法表示函数<i>w</i>=<i>g</i>(<i>x</i>);</p> |
| | | <p>(3) 当销售单价为多少时,该批发商每月可获得最大利润?最大利润是多少?</p> |
| | | <p class="p-btn"> |
| | | <span>(1) 用解析法表示函数<i>y</i>=<i>f</i>(<i>x</i>);</span> |
| | | <span class="btn-box" @click="isShowAnswer38 = !isShowAnswer38"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer38" > |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 设函数<i>y</i>=<i>f</i>(<i>x</i>)的解析式是<i>y</i>=<i>kx</i>+<i>b</i>,则</p> |
| | | <p><math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>40</mn> |
| | | <mi>k</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mn>400</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>50</mn> |
| | | <mi>k</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mn>200</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>,解得<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>k</mi> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mn>20</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mn>1200.</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math></p> |
| | | <p>即<i>y</i>=-20<i>x</i>+1 200.</p> |
| | | <p>根据题意,当30≤<i>x</i>≤60时,函数<i>y</i>=-20<i>x</i>+1 200才有实际意义.</p> |
| | | <p>所以,函数<i>y</i>=<i>f</i>(<i>x</i>)的解析式可表示为</p> |
| | | <p class="center"><i>y</i>=-20<i>x</i>+1 200,30≤<i>x</i>≤60.</p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | <span> |
| | | (2) 该批发商不低于购入价进行销售,设该批发商每月销售这批绿色食品可获得利润为<i>w</i>元,用解析法表示函数<i>w</i>=<i>g</i>(<i>x</i>); |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer39 = !isShowAnswer39"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer39" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(2) 由题意得,<i>w</i>=(<i>x</i>-30)<i>y</i></p> |
| | | <p> =(<i>x</i>-30)(-20<i>x</i>+1 200)</p> |
| | | <p> =-20<i>x</i><sup>2</sup>+1 800<i>x</i>-36 000,</p> |
| | | <p>所以,函数<i>w</i>=<i>g</i>(<i>x</i>)的解析式可表示为</p> |
| | | <p class="center"><i>w</i>=-20<i>x</i><sup>2</sup>+1 800<i>x</i>-36 000,30≤<i>x</i>≤60.</p> |
| | | </div> |
| | | <p class="p-btn"> |
| | | <span> |
| | | (3) 当销售单价为多少时,该批发商每月可获得最大利润?最大利润是多少? |
| | | </span> |
| | | <span class="btn-box" @click="isShowAnswer40 = !isShowAnswer40"> |
| | | <svg xmlns="http://www.w3.org/2000/svg" width="16.501" height="16.501" viewBox="0 0 20.501 20.501"> |
| | | <path class="a" |
| | | d="M3344.717-15308.5H3337.4a10.186,10.186,0,0,1-7.25-3,10.185,10.185,0,0,1-3-7.25A10.262,10.262,0,0,1,3337.4-15329a10.26,10.26,0,0,1,10.249,10.248,10.129,10.129,0,0,1-2.2,6.341v3.177A.734.734,0,0,1,3344.717-15308.5Zm-9.606-7.29h4.493l.527,1.419c.071.182.156.386.254.608a2.428,2.428,0,0,0,.273.512.986.986,0,0,0,.315.262.971.971,0,0,0,.454.1,1.05,1.05,0,0,0,.773-.327,1.025,1.025,0,0,0,.319-.723,3.3,3.3,0,0,0-.277-1.051l-.062-.161-2.889-7.313c-.119-.321-.228-.607-.335-.873a2.972,2.972,0,0,0-.323-.616,1.56,1.56,0,0,0-.5-.469,1.552,1.552,0,0,0-.781-.181,1.535,1.535,0,0,0-.773.181,1.475,1.475,0,0,0-.5.477,3.674,3.674,0,0,0-.362.739l-.239.627-.054.135-2.824,7.355c-.095.229-.179.46-.25.688a1.529,1.529,0,0,0-.073.477.978.978,0,0,0,.323.72,1.039,1.039,0,0,0,.746.315.838.838,0,0,0,.716-.3,4.676,4.676,0,0,0,.466-.985l.062-.165.527-1.449Zm3.747-1.5h-3.293l1.812-5.124,1.481,5.123Z" |
| | | transform="translate(-3327.144 15329)" /> |
| | | </svg> |
| | | </span> |
| | | </p> |
| | | <div v-if="isShowAnswer40" > |
| | | <p> <span class="zt-ls"><b>解</b></span>(3) 由(2) 知,<i>w</i>=-20<i>x</i><sup>2</sup>+1 800<i>x</i>-36 000,30≤<i>x</i>≤60,配方得</p> |
| | | <p class="center"><i>w</i>=-20(<i>x</i>-45)<sup>2</sup>+4 500.</p> |
| | | <p>所以,当<i>x</i>=45时,<i>w</i>的值最大,最大值是4 500.</p> |
| | | <p>答:当销售单价为45元时,该批发商每月可获得最大利润,最大利润是4 500元.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <p class="block"><span |
| | | class="zt-ls2"><b>分析</b></span> 先由图像求出一次函数的解析式,再根据每月所获利润=(销售单价-进价)×每月销售量,列出每月所获利润<i>w</i>与销售单价<i>x</i>的函数关系. |
| | | </p> |
| | | <p><span class="zt-ls"><b>解</b></span>(1) 设函数<i>y</i>=<i>f</i>(<i>x</i>)的解析式是<i>y</i>=<i>kx</i>+<i>b</i>,则</p> |
| | | <p><math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>40</mn> |
| | | <mi>k</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mn>400</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>50</mn> |
| | | <mi>k</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mn>200</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>,解得<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>k</mi> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mn>20</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mn>1200.</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math></p> |
| | | <p>即<i>y</i>=-20<i>x</i>+1 200.</p> |
| | | <p>根据题意,当30≤<i>x</i>≤60时,函数<i>y</i>=-20<i>x</i>+1 200才有实际意义.</p> |
| | | <p>所以,函数<i>y</i>=<i>f</i>(<i>x</i>)的解析式可表示为</p> |
| | | <p class="center"><i>y</i>=-20<i>x</i>+1 200,30≤<i>x</i>≤60.</p> |
| | | <p>(2) 由题意得,<i>w</i>=(<i>x</i>-30)<i>y</i></p> |
| | | <p> =(<i>x</i>-30)(-20<i>x</i>+1 200)</p> |
| | | <p> =-20<i>x</i><sup>2</sup>+1 800<i>x</i>-36 000,</p> |
| | | <p>所以,函数<i>w</i>=<i>g</i>(<i>x</i>)的解析式可表示为</p> |
| | | <p class="center"><i>w</i>=-20<i>x</i><sup>2</sup>+1 800<i>x</i>-36 000,30≤<i>x</i>≤60.</p> |
| | | <p>(3) 由(2) 知,<i>w</i>=-20<i>x</i><sup>2</sup>+1 800<i>x</i>-36 000,30≤<i>x</i>≤60,配方得</p> |
| | | <p class="center"><i>w</i>=-20(<i>x</i>-45)<sup>2</sup>+4 500.</p> |
| | | <p>所以,当<i>x</i>=45时,<i>w</i>的值最大,最大值是4 500.</p> |
| | | <p>答:当销售单价为45元时,该批发商每月可获得最大利润,最大利润是4 500元.</p> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /></p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[110]" :hideCollect="true" sourceType="json" |
| | |
| | | <!-- 112 --> |
| | | <div class="page-box hidePage" page="119"> |
| | | </div> |
| | | <!-- 函数控件弹窗 --> |
| | | <!-- 函数控件弹窗 --> |
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| | | <svg style="position: absolute; right:10px;cursor: pointer;" @click="dialogVisible = false" t="1718596022986" |
| | |
| | | <iframe src="https://www.geogebra.org/calculator" frameborder="0" style="width: 100%; min-height: 800px"></iframe> |
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| | | <span style=""> 解题思路 </span> |
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| | | @close="closeDialog" class="thinkDialog"> |
| | | <div slot="title" class="think-header" |
| | | style="padding: 0; text-align: center; color: #333;display:flex;justify-content: center;"> |
| | | <span style=""> 分析 </span> |
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| | | <span style="position: relative"> |
| | | <span style="position: absolute; top: 16px; left: 13px; color: #fff">{{ index + 1 }}</span> |
| | | <img src="../../assets/images/icon/blue-group.png" alt="" style="margin-right: 10px" |
| | |
| | | <img src="../../assets/images/icon/blue.png" alt="" v-if="index == thinkOne.length - 1" |
| | | style="margin-right: 10px" /> |
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| | | <p class="txt-p">{{ item.txt }}</p> |
| | | <p class="txt-p" v-html="item"></p> |
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| | | <img src="../../assets/images/icon/mouse.png" alt="" v-if="thinkIndex != 3" /> |
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| | | class="icon" viewBox="0 0 1024 1024" version="1.1" p-id="5067" width="15" height="15"> |
| | | <path |
| | | d="M2.257993 493.371555 415.470783 906.584344 512 1003.113561 608.529217 906.584344 1021.742007 493.371555 925.212789 396.842337 512 810.055127 98.787211 396.842337Z" |
| | | fill="#1296db" p-id="5068" /> |
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| | | <span> |
| | | 解题步骤 |
| | | </span> |
| | | <svg style="position: absolute; right:10px;cursor: pointer;" @click="stepDialog = false" t="1718596022986" |
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| | | justify-content: center; |
| | | "> |
| | | <img src="../../assets/images/icon/mouse.png" alt="" v-if="stepIndex != 2" /> |
| | | <img src="../../assets/images/icon/mouse.png" alt="" v-if="showIndex < thinkData.length - 1" /> |
| | | <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" t="1710234570135" |
| | | class="icon" viewBox="0 0 1024 1024" version="1.1" p-id="5067" width="15" height="15"> |
| | | <path |
| | |
| | | import examinations from '@/components/examinations/index.vue' |
| | | import { getResourcePath } from "@/assets/methods/resources"; |
| | | import { getCollectResource, setCollectResource } from "@/assets/methods/resources"; |
| | | const handleShow = (num) => { |
| | | const obj = {} |
| | | for (let index = 0; index < num; index++) { |
| | | obj['isShowAnswer' + index] = false |
| | | } |
| | | return obj |
| | | } |
| | | const showObj = handleShow(50) |
| | | export default { |
| | | name: '', |
| | | props: { |
| | |
| | | components: {examinations,paint}, |
| | | data() { |
| | | return { |
| | | ...showObj, |
| | | collectImg: require("../../assets/images/icon/heart.png"), |
| | | collectCheck: require("../../assets/images/icon/heart-check.png"), |
| | | isShowExampleOne: false, |
| | |
| | | isShowExampleFive: false, |
| | | dialogVisible: false, |
| | | thinkingDialog: false, |
| | | stepDialog: false, |
| | | videoPath: "", |
| | | stepIndex: 1, |
| | | thinkIndex: 1, |
| | |
| | | txtOne: "", |
| | | txtTwo: "", |
| | | }, |
| | | showIndex:0, |
| | | thinkData:[], |
| | | thinkOne: [ |
| | | { |
| | | txt: "1:一个函数是不 是偶函数,可以由 函数的图像是否关 于y 轴 对 称 来 判 断;当函数用解析 法表示时,可以用 偶 函 数 的 定 义 来 判断。 偶函数:一般地,设函数f(x)的定义域为D,如果对于任意xED,都有XED,且f(-x)=f(x),那么函数f(x)就叫作偶函数", |
| | | isShow: true, |
| | | }, |
| | | { |
| | | txt: "2:计算f(-x)", |
| | | isShow: false, |
| | | }, |
| | | { |
| | | txt: "3:判断f(-x)是否等于f(x)", |
| | | isShow: false, |
| | | }, |
| | | "1:一个函数是不 是偶函数,可以由 函数的图像是否关 于y 轴 对 称 来 判 断;当函数用解析 法表示时,可以用 偶 函 数 的 定 义 来 判断。 偶函数:一般地,设函数f(x)的定义域为D,如果对于任意xED,都有XED,且f(-x)=f(x),那么函数f(x)就叫作偶函数", |
| | | "2:计算f(-x)", |
| | | "3:判断f(-x)是否等于f(x)", |
| | | ], |
| | | stepOne: [ |
| | | { |
| | | txt: "1:(1)函数f(x)=3x2+1的定义域是R,对任意XER,都有-XER", |
| | | isShow: true, |
| | | }, |
| | | { |
| | | txt: "2:f(-x)=3(-x)2+1=3x2+1=f(x)", |
| | | isShow: false, |
| | | }, |
| | | thinkTwo:[ |
| | | '因为<i>AB</i>的长度为<i>x</i>(m),<i>BC</i>的长度为(12-<i>x</i>)(m),所以必须满足<i>x</i>>0且12-<i>x</i>>0才有实际意义.' |
| | | ], |
| | | dragQuestion: [ |
| | | { |
| | | analysisCon: null, |
| | | answer: ['A', 'B', 'C'], |
| | | difficulty: 0, |
| | | id: "7BC7B760", |
| | | isCollect: false, |
| | | isComplete: false, |
| | | isRight: null, |
| | | isUnfold: "", |
| | | isUserAnswer: false, |
| | | number: 1, |
| | | option: [ |
| | | { |
| | | img: "", |
| | | index: "010311", |
| | | txt: "胆小的", |
| | | value: "A", |
| | | isShow: true |
| | | }, |
| | | { |
| | | img: "", |
| | | index: "010312", |
| | | txt: "善良的", |
| | | value: "B", |
| | | isShow: true |
| | | }, |
| | | { |
| | | img: "", |
| | | index: "010313", |
| | | txt: "沉稳的", |
| | | value: "C", |
| | | isShow: true |
| | | }, |
| | | ], |
| | | optionStyle: "Txt", |
| | | questionType: "drag", |
| | | score: 2, |
| | | stem: { |
| | | 0: "蚂蚁队长走路昂首挺胸、步伐坚定,它是一只(", |
| | | 1: { |
| | | data: "span", |
| | | num: 0 |
| | | }, |
| | | 2: ")蚂蚁;小蚂蚁走起路来小心翼翼,眼神飘忽不定,它是一只(", |
| | | 3: { |
| | | data: "span", |
| | | num: 1 |
| | | }, |
| | | 4: ")蚂蚁;蚂蚁小妹面带微笑,时刻愿意帮助大家,它是一只(", |
| | | 5: { |
| | | data: "span", |
| | | num: 2, |
| | | }, |
| | | 6: " )蚂蚁" |
| | | }, |
| | | stemStyle: "RichTxt", |
| | | type: "拖拽题", |
| | | userAnswer: [ |
| | | { |
| | | vlaue: '', |
| | | txt: '' |
| | | }, |
| | | { |
| | | vlaue: '', |
| | | txt: '' |
| | | }, |
| | | { |
| | | vlaue: '', |
| | | txt: '' |
| | | }, |
| | | ] |
| | | }, |
| | | thinkThree:[ |
| | | '计算该军舰从出发地驶入海港所需要的时间,就可得到函数<i>s</i>=<i>f</i>(<i>t</i>)的定义域.用解析法表示函数后,再画出函数的图像.' |
| | | ], |
| | | thinkFour:[ |
| | | '首先需明确这个函数的定义域.由于居民用电量不同,其收费标准也不同,所以这是分段函数.其次要厘清自变量<i>x</i>在不同的取值范围内与因变量<i>y</i>之间的对应关系,并列出相应的解析式来解决相关问题.' |
| | | ], |
| | | thinkFive:[ |
| | | '首先求出小李从A城到B城和从B城返回A城共花费的时间,明确函数的定义域.小李去B城和返回A城的过程中,<i>y</i>与<i>x</i>分别对应的解析式不相同,所以该函数需用分段函数表示.' |
| | | ], |
| | | thinkSix:[ |
| | | '首先需要计算备用材料可修建饲养室新墙的总长;因每间饲养室的周长是定值,所以设<i>AB</i>的长为<i>x</i>(m),就可以用含<i>x</i>的代数式表示<i>BC</i>的长;', |
| | | '再用解析法表示总面积<i>y</i>(m<sup>2</sup>)与<i>x</i>(m)的函数关系;然后利用函数的性质来解决问题.' |
| | | ], |
| | | thinkSeven:[ |
| | | '先由图像求出一次函数的解析式,', |
| | | '再根据每月所获利润=(销售单价-进价)×每月销售量,列出每月所获利润<i>w</i>与销售单价<i>x</i>的函数关系.' |
| | | ] |
| | | }; |
| | | }, |
| | |
| | | } |
| | | this.handleChapterData(); |
| | | }, |
| | | openMathDiaolog() { |
| | | openMathDiaolog() { |
| | | this.dialogVisible = true; |
| | | }, |
| | | openThinkingDialog() { |
| | | this.thinkingDialog = true; |
| | | openDialog(queryData) { |
| | | this.thinkData = queryData |
| | | this.thinkingDialog = !this.thinkingDialog |
| | | }, |
| | | showNext(num) { |
| | | const number = this.thinkOne.findIndex((item, index) => index == num); |
| | | this.thinkOne[number].isShow = true; |
| | | if (this.thinkIndex <= 2) { |
| | | this.thinkIndex++; |
| | | } |
| | | closeDialog() { |
| | | this.showIndex = 0 |
| | | }, |
| | | showNextChange(num) { |
| | | const number = this.stepOne.findIndex((item, index) => index == num); |
| | | this.stepOne[number].isShow = true; |
| | | if (this.stepIndex < 2) { |
| | | this.stepIndex++; |
| | | } |
| | | changeNext() { |
| | | if (this.showIndex < this.thinkData.length - 1) this.showIndex = this.showIndex + 1 |
| | | }, |
| | | //资源收藏事件 |
| | | handleCollectResource(id, md5, resourcePath, resourceType, source, resourceName) { |
| | |
| | | </script> |
| | | |
| | | <style lang="less" scoped> |
| | | |
| | | .iframe-box { |
| | | width: 100%; |
| | | min-height: 800px; |
| | | border: 1px solid #00a1e9; |
| | | border-radius: 10px; |
| | | } |
| | | |
| | | li { |
| | | list-style: none; |
| | | } |
| | |
| | | <template> |
| | | <div class="chapter" num="0"> |
| | | <div class="chapter" num="1"> |
| | | <!-- 封面1 --> |
| | | <div class="page-box cover mt-20" page="1"> |
| | | <div v-if="showPageList.indexOf(1) > -1"> |
| | |
| | | <div id="searchDomBox" style="display: none"> |
| | | <div id="searchContent"></div> |
| | | </div> |
| | | <div class="page-content" :style="{ |
| | | fontSize: fontSize ? fontSize + 'px' : '16px', |
| | | transform: `scale(${pageZoom ? pageZoom : 1})`, |
| | | transformOrigin: 'center top', |
| | | }"> |
| | | <pageHeader v-if="showCatalogList.indexOf(0) > -1" :showPageList="loadPageList"></pageHeader> |
| | | <chapterOne v-if="showCatalogList.indexOf(1) > -1" :showPageList="loadPageList" :questionData="questionDataMap"> |
| | | <div |
| | | class="page-content" |
| | | :style="{ |
| | | fontSize: fontSize ? fontSize + 'px' : '16px', |
| | | transform: `scale(${pageZoom ? pageZoom : 1})`, |
| | | transformOrigin: 'center top', |
| | | }" |
| | | > |
| | | <pageHeader |
| | | v-if="showCatalogList.indexOf(1) > -1" |
| | | :showPageList="loadPageList" |
| | | ></pageHeader> |
| | | <chapterOne |
| | | v-if="showCatalogList.indexOf(2) > -1" |
| | | :showPageList="loadPageList" |
| | | :questionData="questionDataMap" |
| | | > |
| | | </chapterOne> |
| | | <chapterTwo v-if="showCatalogList.indexOf(3) > -1" :showPageList="loadPageList" :questionData="questionDataMap"> |
| | | <chapterTwo |
| | | v-if="showCatalogList.indexOf(3) > -1" |
| | | :showPageList="loadPageList" |
| | | :questionData="questionDataMap" |
| | | > |
| | | </chapterTwo> |
| | | <chapterThree v-if="showCatalogList.indexOf(4) > -1" :showPageList="loadPageList" :questionData="questionDataMap"> |
| | | <chapterThree |
| | | v-if="showCatalogList.indexOf(4) > -1" |
| | | :showPageList="loadPageList" |
| | | :questionData="questionDataMap" |
| | | > |
| | | </chapterThree> |
| | | <chapterFour v-if="showCatalogList.indexOf(5) > -1" :showPageList="loadPageList" :questionData="questionDataMap"> |
| | | <chapterFour |
| | | v-if="showCatalogList.indexOf(5) > -1" |
| | | :showPageList="loadPageList" |
| | | :questionData="questionDataMap" |
| | | > |
| | | </chapterFour> |
| | | <chapterFive v-if="showCatalogList.indexOf(6) > -1" :showPageList="loadPageList" :questionData="questionDataMap"> |
| | | <chapterFive |
| | | v-if="showCatalogList.indexOf(6) > -1" |
| | | :showPageList="loadPageList" |
| | | :questionData="questionDataMap" |
| | | > |
| | | </chapterFive> |
| | | |
| | | </div> |
| | | </div> |
| | | </template> |
| | |
| | | import chapterOne from "./chapter001.vue"; |
| | | import chapterTwo from "./chapter002.vue"; |
| | | import chapterThree from "./chapter003.vue"; |
| | | import chapterFour from './chapter004.vue' |
| | | import chapterFive from './chapter005.vue' |
| | | import chapterFour from "./chapter004.vue"; |
| | | import chapterFive from "./chapter005.vue"; |
| | | import NoteIcon from "@/assets/images/biji.png"; |
| | | import _ from "lodash"; |
| | | import Swiper from "swiper/bundle"; |
| | |
| | | highlightData: null, |
| | | questionId: {}, |
| | | collectId: [], |
| | | questionDataIndex: 0, // 当前请求的是哪个章节的题目 |
| | | questionList: [], // 章节题目列表 |
| | | }; |
| | | }, |
| | | computed: { |
| | |
| | | }, |
| | | mounted() { |
| | | // 默认加载章节 |
| | | this.showCatalogList = [0]; |
| | | this.showCatalogList = [1]; |
| | | // 滚动监听节流 |
| | | this.throttledScrollHandler = _.throttle( |
| | | this.scrollFun, |
| | |
| | | }, 500); |
| | | |
| | | // 测试页面跳转 |
| | | setTimeout(() => { |
| | | this.gotoPage(3, 111); |
| | | // setTimeout(() => { |
| | | // this.gotoPage(6,206); |
| | | // // setTimeout(() => { |
| | | // // this.renderSign("Highlight", { |
| | | // // id: "2ACA9359", |
| | |
| | | // // txt: " 运动系统是由骨、骨连结和骨骼肌三部分组成的。全身的骨通过骨连结组成人体骨骼(见图1-1)。骨骼是人体的支架,具有保护内脏器官、供肌肉附着和作为肌肉运动的杠杆等作用。在神经系统的支配下,肌肉收缩牵动所附着的骨绕着关节转动,使身体产生各种动作。所以,运动系统具有运动、支持和保护等功能,幼年时期的骨骼还具有造血功能。 ", |
| | | // // txtIndex: 57 |
| | | // // }); |
| | | }, 500); |
| | | // }, 500); |
| | | |
| | | // 获取题目id列表 |
| | | this.getQuestionId(); |
| | | this.getCollect() |
| | | this.getCollect(); |
| | | }, |
| | | methods: { |
| | | // setZoom1() { |
| | |
| | | // }, |
| | | // 滚动监听 |
| | | scrollFun(event) { |
| | | |
| | | this.handleVideoPicture() |
| | | this.handleVideoPicture(); |
| | | |
| | | // 判断向上滚动还是向下滚动 |
| | | if (event.target.scrollTop > this.previousScrollTop) { |
| | |
| | | this.catalogLength - 2, |
| | | this.catalogLength - 1, |
| | | this.catalogLength, |
| | | |
| | | ]; |
| | | } else { |
| | | this.showCatalogList = [catalog - 1, catalog, catalog + 1]; |
| | |
| | | page && pageThemeColor && pageThemeColor[page] |
| | | ? pageThemeColor[page] |
| | | : chapterNum && chapterThemeColor && chapterThemeColor[chapterNum] |
| | | ? chapterThemeColor[chapterNum] |
| | | : bookThemeColor; |
| | | ? chapterThemeColor[chapterNum] |
| | | : bookThemeColor; |
| | | if (themeColor) { |
| | | domItem.style.color = themeColor; |
| | | } |
| | |
| | | page && pageThemeColor && pageThemeColor[page] |
| | | ? pageThemeColor[page] |
| | | : chapterNum && chapterThemeColor && chapterThemeColor[chapterNum] |
| | | ? chapterThemeColor[chapterNum] |
| | | : bookThemeColor; |
| | | ? chapterThemeColor[chapterNum] |
| | | : bookThemeColor; |
| | | if (themeColor) { |
| | | domItem.style.backgroundColor = themeColor; |
| | | } |
| | |
| | | page && pageThemeColor && pageThemeColor[page] |
| | | ? pageThemeColor[page] |
| | | : chapterNum && chapterThemeColor && chapterThemeColor[chapterNum] |
| | | ? chapterThemeColor[chapterNum] |
| | | : bookThemeColor; |
| | | ? chapterThemeColor[chapterNum] |
| | | : bookThemeColor; |
| | | if (themeColor) { |
| | | domItem.style.borderColor = themeColor; |
| | | } |
| | |
| | | if (!this.questionDataMap[page]) { |
| | | if (this.questionId && this.questionId[catalog]) { |
| | | if (this.questionId[catalog][page]) { |
| | | console.log(page,Array.isArray(this.questionId[catalog][page])); |
| | | if(Array.isArray(this.questionId[catalog][page])) { |
| | | this.questionDataMap[page] = await this.getQuestion(catalog, page,false); |
| | | if (Array.isArray(this.questionId[catalog][page])) { |
| | | this.questionDataMap[page] = await this.getQuestion( |
| | | catalog, |
| | | page, |
| | | false |
| | | ); |
| | | } else { |
| | | const obj = {} |
| | | const obj = {}; |
| | | for (let key in this.questionId[catalog][page]) { |
| | | obj[key] = await this.getQuestion(catalog, page,key) |
| | | obj[key] = await this.getQuestion(catalog, page, key); |
| | | } |
| | | this.questionDataMap[page] = obj |
| | | this.questionDataMap[page] = obj; |
| | | } |
| | | } |
| | | console.log(1, this.questionDataMap); |
| | | } |
| | | } |
| | | // 渲染这一页的标记 |
| | |
| | | // 记录高亮信息 |
| | | this.highlightData = data; |
| | | // 跳转 |
| | | this.gotoPage(data.catalog, data.page, () => { }); |
| | | this.gotoPage(data.catalog, data.page, () => {}); |
| | | }, |
| | | // 获取题目列表 |
| | | getQuestionId() { |
| | |
| | | }, |
| | | // 获取题目收藏id列表 |
| | | getCollect() { |
| | | if(!localStorage.getItem(this.config.tokenKey)) return false |
| | | if (!localStorage.getItem(this.config.tokenKey)) return false; |
| | | this.MG.identity |
| | | .getUserKey({ |
| | | domain: "collectData", |
| | |
| | | try { |
| | | const collect = JSON.parse(res[0].value); |
| | | if (collect.length) { |
| | | this.collectId = collect.find(item => item.type == 'json').collectList |
| | | this.collectId = collect.find( |
| | | (item) => item.type == "json" |
| | | ).collectList; |
| | | } |
| | | } catch (error) { |
| | | console.log("暂无数据"); |
| | | } |
| | | }).catch(res => { |
| | | console.log('index 请求题目收藏id报错'); |
| | | }) |
| | | .catch((res) => { |
| | | console.log("index 请求题目收藏id报错"); |
| | | }); |
| | | }, |
| | | // 获取章节题目 |
| | | async getQuestion(num, page,questionIndex) { |
| | | async getQuestion(num, page, questionIndex) { |
| | | let cardList = [ |
| | | { |
| | | catalogName: "单选题", |
| | |
| | | ]; |
| | | if (this.questionId) { |
| | | if (this.questionId[num] && this.questionId[num][page]) { |
| | | const res = await axios.get( |
| | | this.config.activeBook.resourceUrl + "/question-" + num + ".json" |
| | | ); |
| | | if (!res.data) return []; |
| | | let ids = [] |
| | | questionIndex ? ids = this.questionId[num][page][questionIndex] : ids = this.questionId[num][page] |
| | | for (let index = 0; index < res.data.data.length; index++) { |
| | | const item = res.data.data[index]; |
| | | if (num != this.questionDataIndex) { |
| | | // 判断当前章节的题目json是否已经请求过 |
| | | const res = await axios.get( |
| | | this.config.activeBook.resourceUrl + "/question-" + num + ".json" |
| | | ); |
| | | if (!res.data) return []; |
| | | this.questionList = res.data.data; |
| | | this.questionDataIndex = res.data.chapterNum; |
| | | console.log("章节号", num, res); |
| | | } |
| | | let ids = []; |
| | | questionIndex |
| | | ? (ids = this.questionId[num][page][questionIndex]) |
| | | : (ids = this.questionId[num][page]); |
| | | for (let index = 0; index < this.questionList.length; index++) { |
| | | const item = this.questionList[index]; |
| | | // 数学公式加类名去修改样式 |
| | | if (item.type && item.type == 'material') { |
| | | if (!item.infoList.length) return false |
| | | item.infoList.forEach(citem => { |
| | | if (citem.answer) citem.answer = citem.answer.replace(/\<math/gi, '<math class="examination-math"') |
| | | }) |
| | | if (item.type && item.type == "material") { |
| | | if (!item.infoList.length) return false; |
| | | item.infoList.forEach((citem) => { |
| | | if (citem.answer) |
| | | citem.answer = citem.answer.replace( |
| | | /\<math/gi, |
| | | '<math class="examination-math"' |
| | | ); |
| | | }); |
| | | } else { |
| | | if (item.answer) item.answer = item.answer.replace(/\<math/gi, '<math class="examination-math"') |
| | | if (item.answer) |
| | | item.answer = item.answer.replace( |
| | | /\<math/gi, |
| | | '<math class="examination-math"' |
| | | ); |
| | | } |
| | | item.isCollect = this.collectId.indexOf(item.id) > -1 ? true : false |
| | | item.isCollect = |
| | | this.collectId.indexOf(item.id) > -1 ? true : false; |
| | | if (ids.indexOf(item.id) > -1) { |
| | | if (item.type && item.type == "material") { |
| | | cardList.push(item); |
| | | } else { |
| | | if (item.questionType == "judge") { |
| | | cardList[1].infoList.push(item); |
| | | } |
| | | } |
| | | if (item.questionType == "singleChoice") { |
| | | cardList[0].infoList.push(item); |
| | | } |
| | | if (item.questionType == "multipleChoice") { |
| | | } |
| | | if (item.questionType == "multipleChoice") { |
| | | cardList[2].infoList.push(item); |
| | | } |
| | | if (item.questionType == "completion") { |
| | | } |
| | | if (item.questionType == "completion") { |
| | | cardList[3].infoList.push(item); |
| | | } |
| | | } |
| | | if (item.questionType == "shortAnswer") { |
| | | cardList[4].infoList.push(item); |
| | | } |
| | |
| | | return []; |
| | | } |
| | | }, |
| | | |
| | | // 视频小窗 |
| | | handleVideoPicture() { |
| | | let doms = ( |
| | | this.container ? this.container : document |
| | | ).querySelectorAll(".video"); |
| | | doms = Array.from(doms) |
| | | if (!doms.length) return false |
| | | const playVudio = doms |
| | | .reverse() |
| | | .find((item) => item.paused == false); |
| | | let doms = (this.container ? this.container : document).querySelectorAll( |
| | | ".video" |
| | | ); |
| | | doms = Array.from(doms); |
| | | if (!doms.length) return false; |
| | | const playVudio = doms.reverse().find((item) => item.paused == false); |
| | | if (playVudio) { |
| | | const bottomGap = playVudio.getBoundingClientRect().bottom; |
| | | const topGap = playVudio.getBoundingClientRect().top; |
| | |
| | | playVudio.requestPictureInPicture(); |
| | | } |
| | | } |
| | | } |
| | | }, |
| | | }, |
| | | components: { |
| | | pageHeader, |
New file |
| | |
| | | <template> |
| | | <div ref="ggbContainer" class="ggb-container"></div> |
| | | </template> |
| | | |
| | | <script lang="ts"> |
| | | |
| | | export default { |
| | | mounted() { |
| | | if (!window.GGBApplet) { |
| | | const script = document.createElement("script"); |
| | | script.src = "https://www.geogebra.org/apps/deployggb.js"; |
| | | script.onload = () => { |
| | | this.initGeoGebra(); |
| | | }; |
| | | document.body.appendChild(script); |
| | | } else { |
| | | this.initGeoGebra(); |
| | | } |
| | | }, |
| | | methods:{ |
| | | initGeoGebra() { |
| | | var params = { |
| | | id: "ggbApplet", |
| | | appName: "scientific", |
| | | width: 600, |
| | | height: 600, |
| | | showToolBar: true, |
| | | borderColor: null, |
| | | showMenuBar: true, |
| | | allowStyleBar: true, |
| | | showAlgebraInput: true, |
| | | enableLabelDrags: false, |
| | | enableShiftDragZoom: true, |
| | | capturingThreshold: null, |
| | | showToolBarHelp: false, |
| | | errorDialogsActive: true, |
| | | showTutorialLink: true, |
| | | showLogging: true, |
| | | useBrowserForJS: false, |
| | | }; |
| | | |
| | | if (this.$refs.ggbContainer) { |
| | | const applet = new GGBApplet(params, true); |
| | | applet.inject(this.$refs.ggbContainer); |
| | | } |
| | | } |
| | | } |
| | | } |
| | | |
| | | </script> |
| | | |
| | | <style scoped> |
| | | .ggb-container { |
| | | width: 100%; |
| | | height: 100%; |
| | | /* 其他样式 */ |
| | | } |
| | | </style> |
| | |
| | | <p |
| | | class="titleText text-fl" |
| | | v-if=" |
| | | value.stemStyle == 'Txt' && value.questionType != 'completion' |
| | | value.stemStyle == 'Txt' && value.questionType != 'completion' && value.questionType !='dropdown' |
| | | " |
| | | :id="value.id" |
| | | v-html="value.stem.stemTxt" |
| | |
| | | <span |
| | | v-if="typeof itemText == 'string'" |
| | | v-html="itemText" |
| | | class="input-txt" |
| | | ></span> |
| | | <input |
| | | v-else |
| | |
| | | v-html="value.stem.stemTxt" |
| | | v-cloak |
| | | ></p> |
| | | <!-- 下拉选择题 --> |
| | | <p class="titleText" v-if="value.questionType == 'dropdown'"> |
| | | <span |
| | | v-for="(itemText, indexText) in value.stem" |
| | | :key="indexText + 'questionType'" |
| | | > |
| | | <span |
| | | v-if="typeof itemText == 'string'" |
| | | v-html="itemText" |
| | | class="input-txt" |
| | | ></span> |
| | | <el-select |
| | | v-else |
| | | v-model="value.userAnswer" |
| | | :disabled="value.isComplete" |
| | | > |
| | | <el-option |
| | | v-for="citem in value.option" |
| | | :key="citem.index" |
| | | :label="citem.txt" |
| | | :value="citem.value" |
| | | > |
| | | |
| | | </el-option> |
| | | </el-select> |
| | | </span> |
| | | </p> |
| | | </div> |
| | | <img |
| | | :src="value.isCollect ? isHeart : heart" |
| | |
| | | watch: { |
| | | cardList: { |
| | | handler(newVal) { |
| | | // console.log('新值',newVal); |
| | | this.cardData = this.cardList; |
| | | if (newVal && newVal.length) { |
| | | this.loading = false; |
| | |
| | | this.getErrorList(); |
| | | }, |
| | | methods: { |
| | | // 获取不受保护的图片 |
| | | getPublicImage(md5, width, height) { |
| | | if(!md5) return |
| | | if(md5.includes('http')) return md5 |
| | | let src = null; |
| | | if (md5) { |
| | | src = process.env.VUE_APP_API_URL + `/file/GetPreViewImage?md5=${md5}`; |
| | | } |
| | | if (width) src += `&width=${width}`; |
| | | if (height) src += `&height=${height}`; |
| | | return src; |
| | | }, |
| | | // 数组转为字符串方法 |
| | | arrayToString(data) { |
| | | // 检查是否为数组 |
| | |
| | | } |
| | | } else if ( |
| | | citem.questionType == "singleChoice" || |
| | | citem.questionType == "judge" |
| | | citem.questionType == "judge" || |
| | | citem.questionType == 'dropdown' |
| | | ) { |
| | | if (citem.id == "63825") console.log("i", item); |
| | | citem.isRight = citem.answer == citem.userAnswer; |
| | | } else if (citem.questionType == "shortAnswer") { |
| | | // 简答 翻译 |
| | |
| | | </script> |
| | | |
| | | |
| | | <style lang="less" > |
| | | .titleText img { |
| | | max-width: 80%; |
| | | } |
| | | </style> |
| | | |
| | | <style lang="less" scoped> |
| | | .catalogName { |
| | | text-indent: 1em !important; |
| | |
| | | font-size: 16px; |
| | | line-height: 32px; |
| | | color: #000; |
| | | |
| | | .input-txt { |
| | | display: flex; |
| | | flex-wrap: wrap; |
| | | align-items: center; |
| | | } |
| | | span { |
| | | display: inline-block; |
| | | font-size: 16px; |
| | | // line-height: 26px; |
| | | color: #000; |
| | | font-weight: 400; |
| | | margin-top: 6px; |