| | |
| | | <template> |
| | | <div class="chapter" num="3"> |
| | | |
| | | <!-- 第二单元首页 --> |
| | | <div class="page-box" page="38"> |
| | | <div v-if="showPageList.indexOf(38) > -1"> |
| | | |
| | | <div class="padding-116">第二单元首页</div> |
| | | <h1 id="a006"> |
| | | <img class="img-0" alt="" src="../../assets/images/dy2.jpg" /> |
| | | </h1> |
| | | <div class="padding-116"> |
| | | <p> |
| | | 物体有轻有重,速度有快有慢,气温有高有低,光线有强有弱,面积有大有小……在实际生活中,这种不相等的数量关系无处不在.我们可以利用不等关系构建不等式,并通过不等式解决现实生活中的问题. |
| | | </p> |
| | | <p> |
| | | 例如,随着时代的进步,人们对住宅的要求越来越高.通常人们在选择住宅时,都会考虑采光问题,这就需要把窗户开得尽可能大.按采光标准,窗户的有效透光面积与室内地面面积的比值应不小于 |
| | | <math display="0"> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | </math>,这个比值越大,住宅的采光效果越好. |
| | | </p> |
| | | <p> |
| | | 如果窗户的有效透光面积和室内地面面积同时增加相同的面积,是不是采光效果就会更好呢?解决这样的问题就需要用到有关不等式的知识. |
| | | </p> |
| | | <p> |
| | | 不等式是数学中的重要内容,它具有应用广泛、变换灵活的特点,是研究数量大小关系的必备知识,与数学的其他分支内容有着密切的联系,也是学习高等数学的基础和工具. |
| | | </p> |
| | | <p> |
| | | 本单元在初中学习的基础之上,进一步学习不等式的基本性质、区间、一元二次不等式、含绝对值的不等式等.学习根据数量关系列出相应的不等式,并利用这些不等式找到问题的解决方案,提升数学运算、直观想象、逻辑推理和数学建模等核心素养. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 目标 --> |
| | | <div class="page-box" page="39"> |
| | | <div v-if="showPageList.indexOf(39) > -1"> |
| | | <div class="padding-116">目标</div> |
| | | <div class="padding-116"> |
| | | <p class="left"> |
| | | <img class="inline2" alt="" src="../../assets/images/xxmb.jpg" /> |
| | | </p> |
| | | <div class="fieldset"> |
| | | <p>1.不等式的基本性质.</p> |
| | | <p>(1) 掌握判断两个数(式)大小的“作差比较法”;</p> |
| | | <p>(2) 了解不等式的基本性质.</p> |
| | | <p>2.区间.</p> |
| | | <p>理解区间的概念.</p> |
| | | <p>3.一元二次不等式.</p> |
| | | <p>(1) 了解一元二次不等式的概念;</p> |
| | | <p> |
| | | (2) 了解二次函数、一元二次方程与一元二次不等式三者之间的关系; |
| | | </p> |
| | | <p>(3) 掌握一元二次不等式的解法.</p> |
| | | <p>4.含绝对值的不等式.</p> |
| | | <p> |
| | | (1) |
| | | 了解含绝对值的不等式|<i>x</i>|<<i>a</i>和|<i>x</i>|><i>a</i>(<i>a</i>>0)的含义; |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 掌握形如|<i>ax</i>+<i>b</i>|<<i>c</i>和|<i>ax</i>+<i>b</i>|><i>c</i>(<i>c</i>>0)的不等式的解法. |
| | | </p> |
| | | <p>5.不等式的应用.</p> |
| | | <p> |
| | | 初步掌握从实际问题中抽象出一元二次不等式模型解决简单实际问题的方法. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | |
| | | |
| | | <!-- 033 --> |
| | | <div class="page-box" page="40"> |
| | | <div v-if="showPageList.indexOf(40) > -1"> |
| | |
| | | <p><span>033</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="left"> |
| | | <img class="inline2" alt="" src="../../assets/images/xxmb.jpg" /> |
| | | </p> |
| | | <div class="fieldset"> |
| | | <p>1.不等式的基本性质.</p> |
| | | <p>(1) 掌握判断两个数(式)大小的“作差比较法”;</p> |
| | | <p>(2) 了解不等式的基本性质.</p> |
| | | <p>2.区间.</p> |
| | | <p>理解区间的概念.</p> |
| | | <p>3.一元二次不等式.</p> |
| | | <p>(1) 了解一元二次不等式的概念;</p> |
| | | <p> |
| | | (2) 了解二次函数、一元二次方程与一元二次不等式三者之间的关系; |
| | | </p> |
| | | <p>(3) 掌握一元二次不等式的解法.</p> |
| | | <p>4.含绝对值的不等式.</p> |
| | | <p> |
| | | (1) |
| | | 了解含绝对值的不等式|<i>x</i>|<<i>a</i>和|<i>x</i>|><i>a</i>(<i>a</i>>0)的含义; |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 掌握形如|<i>ax</i>+<i>b</i>|<<i>c</i>和|<i>ax</i>+<i>b</i>|><i>c</i>(<i>c</i>>0)的不等式的解法. |
| | | </p> |
| | | <p>5.不等式的应用.</p> |
| | | <p> |
| | | 初步掌握从实际问题中抽象出一元二次不等式模型解决简单实际问题的方法. |
| | | </p> |
| | | </div> |
| | | <h2 id="b007"> |
| | | 2.1 不等式的基本性质<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <h3 id="c012"> |
| | | 2.1.1 不等式的基本性质<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/zshg.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block">我们知道:</p> |
| | | <p class="block">(1) <i>a</i>><i>b</i>⇔<i>a</i>-<i>b</i>>0;</p> |
| | | <p class="block">(2) <i>a</i>><i>b</i>⇔<i>b</i><<i>a</i>;</p> |
| | | <p class="block"> |
| | | (3) |
| | | 若<i>a</i>><i>b</i>,<i>b</i>><i>c</i>,则<i>a</i>><i>c</i>. |
| | | </p> |
| | | <p class="block">初中我们还学习过不等式的下列性质:</p> |
| | | <p class="block"> |
| | | <b>性质1</b> |
| | | <i>a</i>><i>b</i>⇔<i>a</i>±<i>c</i>><i>b</i>±<i>c</i>. |
| | | </p> |
| | | <p class="block"> |
| | | <b>性质2</b> |
| | | <i>a</i>><i>b</i>,<i>c</i>>0⇒<i>ac</i>><i>bc</i>(或<math display="0"> |
| | | <mfrac> |
| | | <mi>a</mi> |
| | | <mi>c</mi> |
| | | </mfrac> |
| | | <mo>></mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mi>c</mi> |
| | | </mfrac> |
| | | </math>). |
| | | </p> |
| | | <p class="block"> |
| | | <b>性质3</b> |
| | | <i>a</i>><i>b</i>,<i>c</i><0⇒<i>ac</i><<i>bc</i>(或<math display="0"> |
| | | <mfrac> |
| | | <mi>a</mi> |
| | | <mi>c</mi> |
| | | </mfrac> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mi>c</mi> |
| | | </mfrac> |
| | | </math>). |
| | | </p> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/wttc.jpg" /></p> |
| | | <p> |
| | | 有观点认为,最美人体的下半身长(肚脐至脚的触地点的长度)与全身长之比是<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <msqrt> |
| | | <mn>5</mn> |
| | | </msqrt> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <msqrt> |
| | | <mn>5</mn> |
| | | </msqrt> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>≈</mo> |
| | | <mn>0.618</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>,这被称为黄金分割比例.某芭蕾舞演员全身长166cm,下半身长98cm.表演过程中,芭蕾舞演员会立起脚尖跳舞,此时肚脐与脚的触地点的距离增加了8 |
| | | cm.试问:该芭蕾舞演员下半身长与全身长的比值,在脚尖立起前后哪个大? |
| | | 哪一个更接近0.618? |
| | | </p> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /></p> |
| | | <p> |
| | | 该芭蕾舞演员脚尖立起前,下半身长与全身长的比值为<math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | </math>;脚尖立起后,下半身长与全身长的比值为<math display="0"> |
| | | <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>106</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | </math> |
| | | .本题要求比较这两个分数的大小. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 034 --> |
| | | <div class="page-box" page="41"> |
| | | <div v-if="showPageList.indexOf(41) > -1"> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /></p> |
| | | <p> |
| | | 为了借助不等式知识解决上面的问题,我们需要进一步研究不等式的性质.根据初中学过的不等式的3个基本性质,可以得到一系列推论. |
| | | </p> |
| | | <p>根据性质1,可得下列推论.</p> |
| | | <p> |
| | | <b>推论1</b> |
| | | <i>a</i>><i>b</i>,<i>c</i>><i>d</i>⇒<i>a</i>+<i>c</i>><i>b</i>+<i>d</i>. |
| | | </p> |
| | | <p><b>证明</b> 根据性质1,可知</p> |
| | | <p class="center"> |
| | | <i>a</i>><i>b</i>⇒<i>a</i>+<i>c</i>><i>b</i>+<i>c</i>, |
| | | </p> |
| | | <p class="center"> |
| | | <i>c</i>><i>d</i>⇒<i>c</i>+<i>b</i>><i>d</i>+<i>b</i>,即<i>b</i>+<i>c</i>><i>b</i>+<i>d</i>. |
| | | </p> |
| | | <p> |
| | | 从而<i>a</i>+<i>c</i>><i>b</i>+<i>c</i>><i>b</i>+<i>d</i>,即<i>a</i>+<i>c</i>><i>b</i>+<i>d</i>. |
| | | </p> |
| | | <p>例如,5>1,3>-2,根据推论1,有5+3>1+(-2),即8>-1.</p> |
| | | <p> |
| | | <b>推论2</b> <i>a</i>+<i>b</i>><i>c</i>⇒<i>a</i>><i>c</i>-<i>b</i>. |
| | | </p> |
| | | <p>根据性质2,可得下列推论.</p> |
| | | <p> |
| | | <b>推论3</b> |
| | | <i>a</i>><i>b</i>>0,<i>c</i>><i>d</i>>0⇒<i>ac</i>><i>bd</i>. |
| | | </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[41]" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | </div> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 已知<i>a</i>><i>b</i>>0. |
| | | </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 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 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> |
| | | <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> |
| | | <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> |
| | | <!-- 035 --> |
| | |
| | | <p><span>035</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /></p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[42]" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | </div> |
| | | <h3 id="c013">2.1.2 作差比较法<span class="fontsz2">>>></span></h3> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /></p> |
| | | <p> |
| | | 我们知道实数可以比较大小.数学中经常用下面的等价关系比较<i>a</i>,<i>b</i>的大小. |
| | | </p> |
| | | <p class="center"><i>a</i>-<i>b</i>>0⇔<i>a</i>><i>b</i>;</p> |
| | | <p class="center"><i>a</i>-<i>b</i><0⇔<i>a</i><<i>b</i>;</p> |
| | | <p class="center"><i>a</i>-<i>b</i>=0⇔<i>a</i>=<i>b</i>.</p> |
| | | <p> |
| | | 由此可见,比较<i>a</i>,<i>b</i>的大小,只要判断它们的差<i>a</i>-<i>b</i>与0的大小关系即可. |
| | | </p> |
| | | <p> |
| | | 例如,我们可以作差比较<i>a</i><sup>2</sup>+1与2<i>a</i>的大小(<i>a</i>≠1). |
| | | </p> |
| | | <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 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> |
| | | <div v-if="isShowAnswer4"> |
| | | <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> |
| | | <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> |
| | | <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> |
| | | </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> |
| | | </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"> |
| | | 本例中,作差时也可以这样计算: |
| | | <math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>106</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>1</mn> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>68</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>-</mo> |
| | | </math> |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 036 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <div class="bk"> |
| | | <p class="block"> |
| | | <math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>1</mn> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>68</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>68</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>68</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | </math> |
| | | .因为分子相同时,分母越大,分数越小,所以 |
| | | <math display="0"> |
| | | <mfrac> |
| | | <mn>98</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>106</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>68</mn> |
| | | <mn>174</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>68</mn> |
| | | <mn>166</mn> |
| | | </mfrac> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | </math>. |
| | | </p> |
| | | </div> |
| | | <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> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>与<math display="0"> |
| | | <mfrac> |
| | | <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> |
| | | <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> |
| | | </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> |
| | | <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> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <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> |
| | | <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> |
| | | </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> |
| | | </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>+</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> |
| | | <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> |
| | | </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[43] ? questionData[43][1] : []" :hideCollect="true" sourceType="json" |
| | | 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[43] ? questionData[43][2] : []" :hideCollect="true" sourceType="json" |
| | | inputBc="#d3edfa" v-if="questionData"></examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 037 --> |
| | |
| | | <p><span>037</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c014">习题2.1<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[44]" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | </div> |
| | | <h2 id="b008">2.2 区间<span class="fontsz1">>>>>>>>></span></h2> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"><img class="img-gn1" alt="" src="../../assets/images/gn.jpg" /></p> |
| | | </div> |
| | | <p class="block">闭区间</p> |
| | | <p class="block">开区间</p> |
| | | <p class="block">左闭右开区间</p> |
| | | <p class="block">左开右闭区间</p> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /></p> |
| | | <p> |
| | | 以不等式表示元素共同特征的数集,还有一种更为简单的表示方法,叫<b>作区间表示法</b>. |
| | | </p> |
| | | <p>设<i>a</i><<i>b</i>,我们规定:</p> |
| | | <p> |
| | | (1) |
| | | 满足不等式<i>a</i>≤<i>x</i>≤<i>b</i>的<i>x</i>的集合叫作<b>闭区间</b>,表示为 |
| | | [<i>a</i>,<i>b</i>]. |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 满足不等式<i>a</i><<i>x</i><<i>b</i>的<i>x</i>的集合叫作<b>开区间</b>,表示为(<i>a</i>,<i>b</i>). |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 038 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | (3) |
| | | 满足不等式<i>a</i>≤<i>x</i><<i>b</i>和<i>a</i><<i>x</i>≤<i>b</i>的<i>x</i>的集合分别叫作<b>左闭右开区间</b>和<b>左开右闭区间</b>,分别表示为 |
| | | [<i>a</i>,<i>b</i>),(<i>a</i>,<i>b</i>]. |
| | | </p> |
| | | <p> |
| | | 这里的<i>a</i>与<i>b</i>都叫作相应区间的端点.这些区间还可以用数轴表示(如表2-1所示).在数轴上,用实心点表示包括在区间内的端点,用空心点表示不包括在区间内的端点. |
| | | </p> |
| | | <p class="img">表2-1</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0049-1.jpg" /></p> |
| | | <p> |
| | | 实数集<b>R</b>可以用区间表示为(-∞,+∞).符号“∞”读作“无穷大”,它不是一个具体的数,仅表示某个量在变化时,绝对值无限增大的趋势.“+∞”读作“正无穷大”,表示某个量沿正方向无限增大;“-∞”读作“负无穷大”,表示某个量沿负方向无限变化,其绝对值无限增大. |
| | | </p> |
| | | <p> |
| | | 我们还可以把满足<i>x</i>≥<i>a</i>,<i>x</i>><i>a</i>,<i>x</i>≤<i>b</i>,<i>x</i><<i>b</i>的<i>x</i>的集合用区间分别表示为 |
| | | [<i>a</i>,+∞),(<i>a</i>,+∞),(-∞,<i>b</i>],(-∞,<i>b</i>),如表2-2所示. |
| | | </p> |
| | | <p class="img">表2-2</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0049-2.jpg" /></p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 039 --> |
| | |
| | | <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"></div> |
| | | <div class="padding-116"> |
| | | <div class="bk mt-80"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/tbts.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"> |
| | | 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 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> |
| | | (3) |
| | | <math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mo stretchy="false">|</mo> |
| | | </mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>≤</mo> |
| | | <mi>x</mi> |
| | | <mo><</mo> |
| | | <mn>4</mn> |
| | | <mo data-mjx-texclass="CLOSE">}</mo> |
| | | </mrow> |
| | | </math>;(4) |
| | | <math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mo stretchy="false">|</mo> |
| | | </mrow> |
| | | <mo>−</mo> |
| | | <mn>6</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo>≤</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">}</mo> |
| | | </mrow> |
| | | </math>; |
| | | </p> |
| | | <p>(5) {<i>x</i>|<i>x</i>≥2};(6) {<i>x</i>|<i>x</i><1}.</p> |
| | | <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> |
| | | <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> |
| | | <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 class="bj"> |
| | | <examinations :cardList="questionData[47] ? questionData[47][1] : []" :hideCollect="true" sourceType="json" |
| | | inputBc="#d3edfa" v-if="questionData"></examinations> |
| | | </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> |
| | | </div> |
| | | <h2 id="b009"> |
| | | 2.3 一元二次不等式<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <h3 id="c016"> |
| | | 2.3.1 一元二次不等式的概念<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/wttc.jpg" /></p> |
| | | <p class="center"><b>汽车急刹车的停车距离</b></p> |
| | | <p> |
| | | 随着人民生活质量的提高,人们的购车意愿上升.2021年末全国民用汽车保有量30 |
| | | 151万辆,比2020年末增加2 |
| | | 064万辆.在此背景下,汽车行驶安全越发需要引起人们的重视。汽车行驶的过程中,由于惯性的作用,急刹车后会继续向前滑行一段距离才能停住,一般称这段距离为汽车“急刹车的停车距离”.急刹车的停车距离<i>y</i>(m) |
| | | 与车速<i>x</i>(km/h)之间具有确定的关系.不同车型的汽车急刹车的停车距离与车速之间的关系不同,同一车型的汽车急刹车的停车距离与车速之间的关系也会因为天气条件、道路状况等因素的不同而发生变化. |
| | | </p> |
| | | <p> |
| | | 在正常天气条件下,某汽车在高速公路上急刹车的停车距离<i>y</i>(m) |
| | | 与车速<i>x</i>(km/h) |
| | | 之间的函数关系为<i>y</i>=0.007<i>x</i><sup>2</sup>+0.2<i>x</i>,如果希望该汽车急刹车的停车距离不 |
| | | </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</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | </div> |
| | | <div class="page-box hidePage" page="47"> |
| | | </div> |
| | | <!-- 041 --> |
| | | <div class="page-box" page="48"> |
| | | <div v-if="showPageList.indexOf(48) > -1"> |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第二单元 不等式</p> |
| | | </li> |
| | | <li> |
| | | <p><span>041</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | </div> |
| | | <div class="page-box hidePage" page="48"> |
| | | </div> |
| | | <!-- 042 --> |
| | | <div class="page-box" page="49"> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="t0"> |
| | | 超过50m,那么其行驶速度的范围是多少?(注:高速公路上的最低速度为60 |
| | | km/h) |
| | | </p> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /></p> |
| | | <p> |
| | | 上述问题要求“汽车急刹车的停车距离不超过50 |
| | | m”,即y≤50.而该汽车急刹车的停车距离与车速之间的关系为<i>y</i>=0.007<i>x</i><sup>2</sup>+0.2<i>x</i>,因此得到 |
| | | </p> |
| | | <p class="center">0.007<i>x</i><sup>2</sup>+0.2<i>x</i>≤50.</p> |
| | | <p> |
| | | 为了求出行驶速度的范围,我们需要对这个不等式进行求解.这个不等式可以进一步整理为 |
| | | </p> |
| | | <p class="center">0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50≤0.</p> |
| | | <p> |
| | | 这个不等式只含有一个未知数<i>x</i>,并且未知数<i>x</i>的最高次数为2.像这样的不等式还有很多,如2<i>x</i><sup>2</sup>+5<i>x</i>-3<0,3<i>x</i><sup>2</sup>+6<i>x</i>-1>0等. |
| | | </p> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"><img class="img-gn1" alt="" src="../../assets/images/gn.jpg" /></p> |
| | | </div> |
| | | <p class="block">一元二次不等式</p> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /></p> |
| | | <p> |
| | | 一般地,只含有一个未知数,且未知数的最高次数为2的整式不等式,叫作<b>一元二次不等式</b>.一元二次不等式的一般表达式为<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>>0(≥0)或<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i><0(≤0),其中<i>a</i>,<i>b</i>,<i>c</i>均为常数,且<i>a</i>≠0. |
| | | </p> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/zshg.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"><b>1.一元二次方程</b></p> |
| | | <p class="block"> |
| | | 一元二次方程<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>=0(<i>a</i>≠0)的实数解的情况与求解公式如表2-3所示. |
| | | </p> |
| | | <p class="img">表2-3</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0053-1.jpg" /> |
| | | </p> |
| | | <p class="block"> |
| | | 当<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>>0时,有些一元二次方程也可以用因式分解法写成<i>a</i>(<i>x</i>-<i>x</i>1)(<i>x</i>-<i>x</i>2)=0(<i>a</i>≠0),然后再求解. |
| | | </p> |
| | | <p class="block"><b>2.二次函数</b></p> |
| | | <p class="block"> |
| | | 二次函数<i>y</i>=<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>(<i>a</i>≠0)的图像是一条抛物线.当<i>a</i>>0时,抛物线开口向上;当<i>a</i><0时,抛物线开口向下.抛物线与<i>x</i>轴共有3种 |
| | | 位置关系. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 043 --> |
| | |
| | | <p><span>043</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <div class="bk"> |
| | | <p class="block"> |
| | | (1) 当<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>>0时,抛物线与<i>x</i>轴有两个交点; |
| | | </p> |
| | | <p class="block"> |
| | | (2) 当<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=0时,抛物线与<i>x</i>轴只有一个交点; |
| | | </p> |
| | | <p class="block"> |
| | | (3) 当<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i><0时,抛物线与<i>x</i>轴无交点. |
| | | </p> |
| | | <p class="block">抛物线与<i>x</i>轴的3种位置关系如表2-4所示.</p> |
| | | <p class="img">表2-4</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0054-1.jpg" /> |
| | | </p> |
| | | <p class="block"> |
| | | 二次函数<i>y</i>=<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>(<i>a</i>≠0)的图像的对称轴方程为<math display="0"> |
| | | <mi>x</mi> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>,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>,与<i>y</i>轴的交点坐标为(0,<i>c</i>). |
| | | </p> |
| | | </div> |
| | | <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 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> |
| | | <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> |
| | | <!-- 044 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <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> |
| | | </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) 分别画出它们的函数图像;</p> |
| | | <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 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> |
| | | <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> |
| | | </li> |
| | | </ul> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 045 --> |
| | |
| | | <p><span>045</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c017"> |
| | | 2.3.2 一元二次不等式的基本解法<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /></p> |
| | | <p> |
| | | 回到本节开头的问题,如何解不等式0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50≤0呢? |
| | | </p> |
| | | <p> |
| | | 当<i>x</i>变化时,不等式的左边可以看作<i>x</i>的二次函数<i>y</i>=0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50.这样解不等式0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50≤0的问题就可以转化为求二次函数<i>y</i>=0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50的图像上<i>y</i>≤0所对应点的<i>x</i>的取值范围问题. |
| | | </p> |
| | | <p> |
| | | 二次函数<i>y</i>=0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50的图像是开口向上的抛物线.因为<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>=(0.2)<sup>2</sup>-4×0.007×(-50)=1.44>0,所以抛物线与<i>x</i>轴有两个交点,交点的横坐标是方程0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50=0的两个解,解方程0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50=0得<i>x</i>1=-100,<math |
| | | display="0"> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>500</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | </math>.所以图像与<i>x</i>轴的交点坐标为(-100,0),<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>500</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mn>0</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>.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> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>100</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | </math>,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<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>100</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>360</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>. |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0056-6.jpg" /></p> |
| | | <p class="img">图2-4</p> |
| | | <p> |
| | | 故二次函数<i>y</i>=0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50的简图如图2-4所示. |
| | | </p> |
| | | <p>观察图像可知:</p> |
| | | <p> |
| | | 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>1=-100,<math display="0"> |
| | | <msub> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>500</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | </math>; |
| | | </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<math display="0"> |
| | | <mo>−</mo> |
| | | <mn>100</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mn>500</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 故满足不等式0.007<i>x</i><sup>2</sup>+0.2<i>x</i>-50≤0的<i>x</i>所在的区间为<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">[</mo> |
| | | <mo>−</mo> |
| | | <mn>100</mn> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mn>500</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">]</mo> |
| | | </mrow> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 考虑到高速公路上的最低速度为60km/h,如果希望该汽车急刹车的停车距离不超过50m,那么其行驶速度的范围是<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">[</mo> |
| | | <mn>60</mn> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mn>500</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">]</mo> |
| | | </mrow> |
| | | </math>,行驶速度的最大值为<math display="0"> |
| | | <mfrac> |
| | | <mn>500</mn> |
| | | <mn>7</mn> |
| | | </mfrac> |
| | | <mo>≈</mo> |
| | | <mn>71</mn> |
| | | </math>(km/h). |
| | | </p> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /></p> |
| | | <p> |
| | | 一般地,使一元二次不等式成立的值叫作这个<b>一元二次不等式的解</b>. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 046 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="t0"> |
| | | 一元二次不等式的所有解组成的集合,叫作这个<b>一元二次不等式的解集</b>. |
| | | </p> |
| | | <p> |
| | | 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 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> |
| | | <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> |
| | | <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-gn1" alt="" src="../../assets/images/tbts.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"> |
| | | 例(1) |
| | | 中,注意到不等式-<i>x</i><sup>2</sup>+3<i>x</i>+4<0⇔<i>x</i><sup>2</sup>-3<i>x</i>-4>0,从而可将问题转化成解不等式<i>x</i><sup>2</sup>-3<i>x</i>-4>0,即当一元二次不等式的二次项系数为负数时,可以利用不等式的性质将不等式化成二次项系数为正数的一元二次不等式,再求解. |
| | | </p> |
| | | </div> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/tjfx.jpg" /></p> |
| | | <p> |
| | | 通过上面的分析,发现二次函数的图像、一元二次方程的解、一元二次不等式的解集之间有着密切的联系,可以总结成表2-5. |
| | | </p> |
| | | <p class="img">表2-5</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0057-3.jpg" /></p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 047 --> |
| | |
| | | <p><span>047</span></p> |
| | | </li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="img">续表</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0058-1.jpg" /></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[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> |
| | | 一般地,与二次函数<i>y</i>=<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>(<i>a</i>>0)对应的一元二次不等式有四种情形,分别是<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>>0,<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>≥0,<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i><0,<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>≤0.利用二次函数<i>y</i>=<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>(<i>a</i>>0)的图像求解相应的一元二次不等式,可以分为三步. |
| | | </p> |
| | | <p> |
| | | 第一步:确定相应的一元二次方程<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>=0的判别式<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>,从而确定二次函数的图像与<i>x</i>轴的相交情况;如果有交点,则利用方程<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>=0解出交点的横坐标. |
| | | </p> |
| | | <p> |
| | | 第二步:画出二次函数<i>y</i>=<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>的简图. |
| | | </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> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 048 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c018"> |
| | | 2.3.3 特殊类型一元二次不等式的解法<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /></p> |
| | | <p>观察下列不等式:</p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | <p class="right">①</p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | <p class="right">②</p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>≤</mo> |
| | | <mn>0</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | <p class="right">③</p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>≥</mo> |
| | | <mn>0</mn> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p class="right">④</p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0059-5.jpg" /></p> |
| | | <p class="img">图2-7</p> |
| | | <p> |
| | | 以上四个不等式对应的二次函数为<i>y</i>=(<i>x</i>+1)(<i>x</i>-3),对应的一元二次方程为(<i>x</i>+1)(<i>x</i>-3)=0.其解为<i>x</i>1=-1,<i>x</i>2=3.二次函数<i>y</i>=(<i>x</i>+1)(<i>x</i>-3)的图像与<i>x</i>轴有两个交点(-1,0),(3,0). |
| | | </p> |
| | | <p>二次函数<i>y</i>=(<i>x</i>+1)(<i>x</i>-3)的简图如图2-7所示.</p> |
| | | <p> |
| | | 结合二次函数<i>y</i>=(<i>x</i>+1)(<i>x</i>-3)的简图,我们可以得到以下结论. |
| | | </p> |
| | | <p> |
| | | (1) |
| | | 不等式(<i>x</i>+1)(<i>x</i>-3)<0的解在方程(<i>x</i>+1)(<i>x</i>-3)=0的两解之间,解集为(-1,3); |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 不等式(<i>x</i>+1)(<i>x</i>-3)>0的解在方程(<i>x</i>+1)(<i>x</i>-3)=0的两解之外,解集为(-∞,-1)∪(3,+∞); |
| | | </p> |
| | | <p> |
| | | (3) |
| | | 不等式(<i>x</i>+1)(<i>x</i>-3)≤0的解在方程(<i>x</i>+1)(<i>x</i>-3)=0的两解之间,解集为[-1,3]; |
| | | </p> |
| | | <p> |
| | | (4) |
| | | 不等式(<i>x</i>+1)(<i>x</i>-3)≥0的解在方程(<i>x</i>+1)(<i>x</i>-3)=0的两解之外,解集为(-∞,-1]∪[3,+∞). |
| | | </p> |
| | | <p> |
| | | 一般地,一元二次方程(<i>x</i>-<i>p</i>)(<i>x</i>-<i>q</i>)=0(其中<i>p</i>,<i>q</i>为实数,并且<i>p</i><<i>q</i>)有两个不相等的实数解<i>x</i>1=<i>p</i>,<i>x</i>2=<i>q</i>,二次函数<i>y</i>=(<i>x</i>-<i>p</i>)(<i>x</i>-<i>q</i>)的简图如图2-8所示. |
| | | </p> |
| | | <p> |
| | | 观察二次函数<i>y</i>=(<i>x</i>-<i>p</i>)(<i>x</i>-<i>q</i>)的简图,可知下列结论成立. |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0059-6.jpg" /></p> |
| | | <p class="img">图2-8</p> |
| | | <p> |
| | | (1) |
| | | 不等式(<i>x</i>-<i>p</i>)(<i>x</i>-<i>q</i>)<0的解集为(<i>p</i>,<i>q</i>); |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 不等式(<i>x</i>-<i>p</i>)(<i>x</i>-<i>q</i>)>0的解集为(-∞,<i>p</i>)∪(<i>q</i>,+∞); |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 049 --> |
| | |
| | | <p><span>049</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | (3) |
| | | 不等式(<i>x</i>-<i>p</i>)(<i>x</i>-<i>q</i>)≤0的解集为[<i>p</i>,<i>q</i>]; |
| | | </p> |
| | | <p> |
| | | (4) |
| | | 不等式(<i>x</i>-<i>p</i>)(<i>x</i>-<i>q</i>)≥0的解集为(-∞,<i>p</i>]∪[<i>q</i>,+∞). |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 解下列不等式. |
| | | </p> |
| | | <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> |
| | | <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> |
| | | <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 |
| | | </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="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> |
| | | <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> |
| | | <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> |
| | | <examinations :cardList="questionData[56]" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 050 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c019">习题2.3<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[57]" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 051 --> |
| | |
| | | </li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h2 id="b010"> |
| | | 2.4 含绝对值的不等式<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <h3 id="c020"> |
| | | 2.4.1 含绝对值的不等式的基本解法<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/wttc.jpg" /></p> |
| | | <p class="center"><b>商品房预售中的不等式知识</b></p> |
| | | <p> |
| | | 商品房预售时,房地产开发企业将正在建设中的房屋预先出售给购房者, |
| | | 并在购房合同中约定所购买房屋的具体面积(称为“合同约定面积”).房屋竣工后, |
| | | 根据现场实测的房屋面积被称为“产权登记面积”.为保护购房者权益, |
| | | 我国相关法律规定, |
| | | 预售房屋的购房合同中应当写明“合同约定面积”与“产权登记面积”发生误差时的处理方式.合同未作约定的, |
| | | 按以下原则处理:“(一) 面积误差比绝对值在3%以内(含3%) 的, |
| | | 根据‘产权登记面积’结算房价款;(二) |
| | | 面积误差比绝对值超出3%时,购房者有权退房.其中, |
| | | 面积误差比=(产权登记面积-合同约定面积)/合同约定面积×100%.” |
| | | </p> |
| | | <p> |
| | | 李先生购买预售房屋时, 合同约定面积为100 m<sup>2</sup>.房屋竣工后, |
| | | 产权登记面积在什么范围时, 李先生需要根据产权登记面积结算房价款? |
| | | 或者有权退房? |
| | | </p> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/zshg.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"> |
| | | 1.绝对值定义:数轴上表示数<i>a</i>的点与原点之间的距离叫作数<i>a</i>的绝对值,记作|<i>a</i>|. |
| | | </p> |
| | | <p class="block"> |
| | | 2.一个正数的绝对值是它本身;一个负数的绝对值是它的相反数;0的绝对值是0,即 |
| | | </p> |
| | | <p class="block"> |
| | | <math display="0"> |
| | | <mo stretchy="false">|</mo> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo stretchy="false">|</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>a</mi> |
| | | <mo>,</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mi>a</mi> |
| | | <mo>=</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>−</mo> |
| | | <mi>a</mi> |
| | | <mo>,</mo> |
| | | <mi>a</mi> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>,也可以写成<math display="0"> |
| | | <mo stretchy="false">|</mo> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo stretchy="false">|</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>a</mi> |
| | | <mo>,</mo> |
| | | <mi>a</mi> |
| | | <mo>≥</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>−</mo> |
| | | <mi>a</mi> |
| | | <mo>,</mo> |
| | | <mi>a</mi> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | </mtd> |
| | | <mtd></mtd> |
| | | <mtd></mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>. |
| | | </p> |
| | | <p class="block"> |
| | | 3.设<i>a</i>>0,数轴上与原点的距离是<i>a</i>的点有两个,它们分别在原点两侧,分别是-<i>a</i>和<i>a</i>,如图2-9所示. |
| | | </p> |
| | | <p class="center"> |
| | | <img class="img-c" alt="" src="../../assets/images/0062-3.jpg" /> |
| | | </p> |
| | | <p class="img">图2-9</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 052 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /></p> |
| | | <p> |
| | | 假设产权登记面积为<i>x</i>(m<sup>2</sup>),上述问题可用一个含有绝对值的不等式表示. |
| | | </p> |
| | | <math display="block"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">|</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>100</mn> |
| | | </mrow> |
| | | <mn>100</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">|</mo> |
| | | </mrow> |
| | | <mo>≤</mo> |
| | | <mn>3%</mn> |
| | | <mo>,或</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">|</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>100</mn> |
| | | </mrow> |
| | | <mn>100</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">|</mo> |
| | | </mrow> |
| | | <mo>></mo> |
| | | <mn>3%</mn> |
| | | <mo>,</mo> |
| | | </math> |
| | | <p>可化为 |<i>x</i>-100|≤3,或|<i>x</i>-100|>3.</p> |
| | | <p>如果我们能解出这两个不等式,就能回答上述问题.</p> |
| | | <p>那么,如何解这种含有绝对值的不等式呢?我们先从简单的情形开始分析.</p> |
| | | <p> |
| | | 设<i>a</i>>0,由绝对值的意义可知,含有绝对值的方程|<i>x</i>|=<i>a</i>的解是<i>x</i>=<i>a</i>或<i>x</i>=-<i>a</i>.那么,含有绝对值的不等式(如|<i>x</i>|≥<i>a</i>,|<i>x</i>|><i>a</i>,|<i>x</i>|≤<i>a</i>,|<i>x</i>|<<i>a</i>等) |
| | | 怎么解呢?下面以不等式|<i>x</i>|≤<i>a</i>(<i>a</i>>0) |
| | | 和|<i>x</i>|><i>a</i>(<i>a</i>>0)为例进行分析. |
| | | </p> |
| | | <p> |
| | | 由绝对值的几何意义,|<i>x</i>|表示实数<i>x</i>对应的点与原点之间的距离.因此,不等式|<i>x</i>|≤<i>a</i>(<i>a</i>>0) |
| | | 表示数轴上到原点的距离不大于<i>a</i>的点的集合.在数轴上,满足|<i>x</i>|≤<i>a</i>(<i>a</i>>0) |
| | | 的实数<i>x</i>对应的点如图2-10所示. |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0063-2.jpg" /></p> |
| | | <p class="img">图2-10</p> |
| | | <p> |
| | | 所以不等式|<i>x</i>|≤<i>a</i>(<i>a</i>>0) |
| | | 的解集是{<i>x</i>|-<i>a</i>≤<i>x</i>≤<i>a</i>},用区间表示为[-<i>a</i>,<i>a</i>]. |
| | | </p> |
| | | <p> |
| | | 同理,不等式|<i>x</i>|><i>a</i>(<i>a</i>>0) |
| | | 表示数轴上到原点的距离大于<i>a</i>的点的集合.在数轴上,满足|<i>x</i>|><i>a</i>(<i>a</i>>0)的实数<i>x</i>对应的点如图2-11所示. |
| | | </p> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0063-3.jpg" /></p> |
| | | <p class="img">图2-11</p> |
| | | <p> |
| | | 所以不等式|<i>x</i>|><i>a</i>(<i>a</i>>0) 的解集是 |
| | | {<i>x</i>|<i>x</i><-<i>a</i>或<i>x</i>><i>a</i>},用区间表示为(-∞,-<i>a</i>)∪(<i>a</i>,+∞). |
| | | </p> |
| | | <p>由此,可以得到表2-6.</p> |
| | | <p class="img">表2-6</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0063-4.jpg" /></p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 053 --> |
| | |
| | | <p><span>053</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <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> |
| | | <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> |
| | | <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> |
| | | <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> |
| | | </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> |
| | | </div> |
| | | <h3 id="c021"> |
| | | 2.4.2 |
| | | |<i>ax</i>+<i>b</i>|<<i>c</i>和|<i>ax</i>+<i>b</i>|><i>c</i>(<i>c</i>>0)的解法<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"><img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /></p> |
| | | <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 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> |
| | | <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> |
| | | <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> |
| | | <!-- 054 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <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> |
| | | <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> |
| | | <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" |
| | | v-if="questionData"></examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 055 --> |
| | |
| | | <p><span>055</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c022">习题2.4<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[62]" :hideCollect="true" sourceType="json" inputBc="#d3edfa" |
| | | v-if="questionData"></examinations> |
| | | </div> |
| | | <h2 id="b011"> |
| | | 2.5 不等式的应用<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <h3 id="c023"> |
| | | 2.5.1 不等式的简单应用<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="center"><img class="img-c" alt="" src="../../assets/images/0066-11.jpg" /></p> |
| | | <p class="img">图2-12</p> |
| | | <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 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> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 056 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <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" |
| | | 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> |
| | | <div class="bk mt-60" > |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/tbts.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"> |
| | | 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> |
| | | <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"> |
| | | <img class="img-gn2" alt="" src="../../assets/images/hzjl.jpg" /> |
| | | </p> |
| | | </div> |
| | | <examinations :cardList="questionData[63]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 057 --> |
| | |
| | | <p><span>057</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"> |
| | | <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"> |
| | | </examinations> |
| | | </div> |
| | | <h3 id="c024"> |
| | | 2.5.2 不等式与复杂实际问题<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <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> |
| | | <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> |
| | | |
| | | <div class="padding-116"></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"> |
| | | <mi>B</mi> |
| | | <mi>M</mi> |
| | | <mi>I</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mo>体重</mo> |
| | | </mrow> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>身高</mo> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | </math>(BMI单位:kg/m<sup>2</sup>).一项研究指出,中职学生身体质量指数与身体素质之间存在一定的关系.研究中使用身体素质指标来衡量学 |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 058 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | 生的身体素质,该指标是指学生参加50m跑,立定跳远,力量(男生引体向上、女生1分钟仰卧起坐),耐力跑(男生1 |
| | | 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 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> |
| | | <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> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 059 --> |
| | |
| | | <p>第二单元 不等式</p> |
| | | </li> |
| | | <li> |
| | | <p><span>059</span></p> |
| | | <p><span>059-060</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="left"> |
| | | <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> |
| | | </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> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 060 --> |
| | | <div class="page-box" page="67"> |
| | | <div v-if="showPageList.indexOf(67) > -1"> |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>060</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | </div> |
| | | <div class="page-box hidePage" page="67"> |
| | | |
| | | </div> |
| | | <!-- 061 --> |
| | | <div class="page-box" page="68"> |
| | |
| | | <p><span>061</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h2 id="b012">数学园地<span class="fontsz1">>>>>>>>></span></h2> |
| | | <p> |
| | | 本单元中,我们学习了不等式的一些性质,以及如何解一元二次不等式和含绝对值的不等式.实际上,数学领域中还有很多不等式,也被用来解决生产生活中的实际问题.尤其是微积分体系建立以前,不等式是计算最大值和最小值问题的最佳工具.下面我们介绍一些著名的不等式. |
| | | </p> |
| | | <p> |
| | | 填写表2-8,并观察<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </math>,<math display="0"> |
| | | <msqrt> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | </msqrt> |
| | | </math>,<math display="0"> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>a</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>这三个数的大小关系. |
| | | </p> |
| | | <p class="img">表2-8</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0072-4.jpg" /></p> |
| | | <p> |
| | | 填写表2-9,并观察<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </math>,<math display="0"> |
| | | <mroot> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | </math>,<math display="0"> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>a</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>这三个数的大小关系. |
| | | </p> |
| | | <p class="img">表2-9</p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0072-8.jpg" /></p> |
| | | <p>通过填写和观察上面两个表格,你有什么发现和猜想?</p> |
| | | <p>实际上,若<i>a</i>,<i>b</i>,<i>c</i>均为正数,则可给出如下定义.</p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </math>叫作<i>a</i>,<i>b</i>两数的算术平均数,<math display="0"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </math>叫作<i>a</i>,<i>b</i>,<i>c</i>三数的算术平均数; |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 062 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | (2) |
| | | <math display="0"> |
| | | <msqrt> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | </msqrt> |
| | | </math>叫作<i>a</i>,<i>b</i>两数的几何平均数,<math display="0"> |
| | | <mroot> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | </math>叫作<i>a</i>,<i>b</i>,<i>c</i>三数的几何平均数; |
| | | </p> |
| | | <p> |
| | | (3) |
| | | <math display="0"> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>a</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>叫作<i>a</i>,<i>b</i>两数的调和平均数,<math display="0"> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>a</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>c</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>叫作<i>a</i>,<i>b</i>,<i>c</i>三数的调和平均数. |
| | | </p> |
| | | <p>观察上面两个表格,可以发现</p> |
| | | <math display="block"> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>⩾</mo> |
| | | <msqrt> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | </msqrt> |
| | | <mo>⩾</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>a</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>+</mo> |
| | | <mi>b</mi> |
| | | <mo>+</mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>⩾</mo> |
| | | <mroot> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mi>b</mi> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>⩾</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>a</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>b</mi> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>c</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p> |
| | | 大胆地想一想,对于<i>n</i>个正数的算术平均数、几何平均数、调和平均数,怎样用符号表示?它们的大小关系能确定吗? |
| | | </p> |
| | | <p> |
| | | 一般地,若<i>a</i>1,<i>a</i>2,<i>a</i>3,…,<i>an</i>为<i>n</i>个正数,则有 |
| | | </p> |
| | | <math display="block"> |
| | | <mfrac> |
| | | <mrow> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>+</mo> |
| | | <mo>⋯</mo> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msub> |
| | | </mrow> |
| | | <mi>n</mi> |
| | | </mfrac> |
| | | <mo>⩾</mo> |
| | | <mroot> |
| | | <mrow> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msub> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo>⋯</mo> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msub> |
| | | </mrow> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mo>⩾</mo> |
| | | <mfrac> |
| | | <mi>n</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msub> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mo>⋯</mo> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msub> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msub> |
| | | </mfrac> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p> |
| | | 其中,当<i>a</i><sub>1</sub>=<i>a</i><sub>1</sub>=<i>a</i><sub>1</sub>=…=<i>an</i>时,等号成立. |
| | | </p> |
| | | <p> |
| | | 随着学习的进一步深入,我们就能够证明数学史上这个著名的不等式,并且知道它的广泛应用. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 063 --> |
| | |
| | | <p><span>063</span></p> |
| | | </li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h2 id="b013">单元小结<span class="fontsz1">>>>>>>>></span></h2> |
| | | <p class="bj2"><b>学习导图</b></p> |
| | | <p class="center"><img class="img-a" alt="" src="../../assets/images/0074-1.jpg" /></p> |
| | | <p class="bj2"><b>学习指导</b></p> |
| | | <p>1.不等式的基本性质.</p> |
| | | <p>(1) 比较数(式)的大小常用“作差比较法”.</p> |
| | | <p>(2) 运用不等式的性质时,要注意验证条件是否都满足.</p> |
| | | <p>2.区间.</p> |
| | | <p> |
| | | 区间是集合的一种表示形式,主要包括开区间、闭区间、左开右闭区间和右开左闭区间. |
| | | </p> |
| | | <p>3.一元二次不等式.</p> |
| | | <p> |
| | | (1) 将一元二次不等式统一化成<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>>0(≥0) |
| | | 或<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i><0(≤0) |
| | | 的形式. |
| | | </p> |
| | | <p> |
| | | (2) 若<i>a</i>>0,此时二次函数的图像开口向上,计算判别式<i>Δ</i>=<i>b</i><sup>2</sup>-4<i>ac</i>. |
| | | </p> |
| | | <p> |
| | | ①当<i>Δ</i>>0时,二次函数的图像与<i>x</i>轴有两个不同的交点(<i>x</i><sub>1</sub>,0),(<i>x</i><sub>2</sub>,0)(<i>x</i><sub>1</sub><<i>x</i><sub>2</sub>).画出函数简图,可得如下结论. |
| | | </p> |
| | | <p> |
| | | <i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>>0的解集为(-∞,<i>x</i><sub>1</sub>)∪(<i>x</i><sub>2</sub>,+∞); |
| | | </p> |
| | | <p> |
| | | <i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>≥0的解集为(-∞,<i>x</i><sub>1</sub>]∪[<i>x</i><sub>2</sub>,+∞); |
| | | </p> |
| | | <p> |
| | | <i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i><0的解集为(<i>x</i><sub>1</sub>,<i>x</i><sub>2</sub>); |
| | | </p> |
| | | <p> |
| | | <i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>≤0的解集为 [<i>x</i><sub>1</sub>,<i>x</i><sub>2</sub>]. |
| | | </p> |
| | | <p> |
| | | ②当<i>Δ</i>=0时,二次函数的图像与<i>x</i>轴只有一个交点(<i>x</i><sub>0</sub>,0).画出函数简图,可得如下结论. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 064 --> |
| | |
| | | <li>上册</li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | <i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>>0的解集为(-∞,<i>x</i><sub>0</sub>)∪(<i>x</i><sub>0</sub>,+∞); |
| | | </p> |
| | | <p><i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>≥0的解集为<b>R</b>;</p> |
| | | <p><i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i><0的解集为 ∅;</p> |
| | | <p> |
| | | <i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>≤0的解集为 {<i>x</i>|<i>x</i>=<i>x</i><sub>0</sub>}. |
| | | </p> |
| | | <p> |
| | | ③当<i>Δ</i><0时,二次函数的图像与<i>x</i>轴没有交点.画出函数简图,可得如下结论. |
| | | </p> |
| | | <p> |
| | | <i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>>0和<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>≥0的解集均为<b>R</b>; |
| | | </p> |
| | | <p> |
| | | <i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i><0和<i>ax</i><sup>2</sup>+<i>bx</i>+<i>c</i>≤0的解集均为 ∅. |
| | | </p> |
| | | <p> |
| | | (3) |
| | | 若<i>a</i><0,则可以转化为-<i>ax</i><sup>2</sup>-<i>bx</i>-<i>c</i>>0(≥0)或-<i>ax</i><sup>2</sup>-<i>bx</i>-<i>c</i><0(≤0)的情形,然后再按步骤(2) |
| | | 的方法进行求解. |
| | | </p> |
| | | <p>4.含绝对值的不等式.</p> |
| | | <p> |
| | | (1) |
| | | 不等式|<i>x</i>|≤<i>a</i>(<i>a</i>>0)的解集是{<i>x</i>|-<i>a</i>≤<i>x</i>≤<i>a</i>},用区间表示为[-<i>a</i>,<i>a</i>]. |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 不等式|<i>x</i>|><i>a</i>(<i>a</i>>0)的解集是{<i>x</i>|<i>x</i><-<i>a</i>或<i>x</i>><i>a</i>},用区间表示为(-∞,-<i>a</i>)∪(<i>a</i>,+∞). |
| | | </p> |
| | | <p> |
| | | (3) |
| | | 求解形如|<i>ax</i>+<i>b</i>|<<i>c</i>和|<i>ax</i>+<i>b</i>|><i>c</i>(<i>c</i>>0)的不等式时,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>5.不等式的应用.</p> |
| | | <p> |
| | | (1) |
| | | 在解决问题的过程中体验如何使用二次函数的图像直观地得出一元二次不等式的解集,学会利用数形结合的思想方法解决问题. |
| | | </p> |
| | | <p>(2) 应用一元二次不等式解决实际问题时,要注意未知量的实际意义.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 065 --> |
| | | <div class="page-box" page="72"> |
| | | <div v-if="showPageList.indexOf(72) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第二单元 不等式</p> |
| | | </li> |
| | | <li> |
| | | <p><span>065</span></p> |
| | | <p><span>065-066</span></p> |
| | | </li> |
| | | </ul> |
| | | |
| | | <div class="padding-116">72</div> |
| | | <div class="padding-116"> |
| | | <h2 id="b014">单元检测<span class="fontsz1">>>>>>>>></span></h2> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[72]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 066 --> |
| | | <div class="page-box" page="73"> |
| | | <div v-if="showPageList.indexOf(73) > -1"> |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>066</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116">73</div> |
| | | </div> |
| | | <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 { |
| | | name: '', |
| | | name: "", |
| | | props: { |
| | | showPageList: { |
| | | type: Array, |
| | | default: [], |
| | | }, |
| | | questionData: { |
| | | type: Object, |
| | | }, |
| | | }, |
| | | components: {}, |
| | | components: { examinations, paint }, |
| | | data() { |
| | | return {} |
| | | return { |
| | | 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 |
| | | }; |
| | | }, |
| | | computed: {}, |
| | | watch: {}, |
| | | created() { }, |
| | | 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> |
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| | | <style lang="less" scoped> |
| | | .pr { |
| | | position: relative; |
| | | } |
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| | | .pa-bk { |
| | | position: absolute; |
| | | right: 45px; |
| | | top: 0; |
| | | width: 140px; |
| | | } |
| | | |
| | | .question-textarea { |
| | | margin-left: 20px; |
| | | width: 94%; |
| | | border-color: #DCDFE6; |
| | | } |
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| | | .table-answer-box { |
| | | math { |
| | | width: max-content; |
| | | height: 36px; |
| | | } |
| | | } |
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| | | li { |
| | | list-style: none; |
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