| | |
| | | <template> |
| | | <div class="chapter" num="5"> |
| | | |
| | | <div class="chapter" num="4"> |
| | | <!-- 第四单元首页 --> |
| | | <div class="page-box" page="120"> |
| | | <div v-if="showPageList.indexOf(120) > -1"> |
| | | <div class="padding-116">第四单元首页</div> |
| | | <h1 id="a008"> |
| | | <img class="img-0" alt="" src="../../assets/images/dy4.jpg" /> |
| | | </h1> |
| | | <div class="padding-116"> |
| | | <p> |
| | | 知识改变命运,技能成就人生,全社会坚持尊重劳动、尊重知识、尊重人才、尊重创造.著名厨师厉恩海曾是一名军人,练就了一身拉面绝活,他能把1 |
| | | kg |
| | | 的面拉出200多万根细如发丝的面条,4次创造吉尼斯世界纪录,被誉为“中国拉面大王”.拉面从一块面块开始,手握两端,两臂均匀用力加速向外抻拉,然后两头对折后再拉,每对折1次,面条的数量在原有基础上翻一倍,如此继续,每次对折后面条的数量形成下列数字1,2,4,8,16,32,64,…为了更好地体现面条数量与对折次数的关系,也可以表示为2<sup>0</sup>,2<sup>1</sup>,2<sup>2</sup>,2<sup>3</sup>,2<sup>4</sup>,2<sup>5</sup>,2<sup>6</sup>,…若用函数语言刻画这类数量关系和变化规律,就是我们即将学习的指数函数.现实生活中,数据量的爆炸式增长、细胞分裂、碳14考古、储蓄利率(复利)、血液中的酒精含量等问题,都会用到指数函数相关知识. |
| | | </p> |
| | | <p> |
| | | 指数函数与对数函数是两类基本初等函数,是提高数学运算能力、培养数形结合思想和数学建模能力的重要内容.它们在人口增长统计、文物考古鉴别、航海卫星定位等方面发挥着重要作用,在财经、金融、公共服务、信息技术等领域有广泛应用. |
| | | </p> |
| | | <p> |
| | | 本单元我们将在整数幂的基础上推广幂的概念,学习实数幂的相关定义和运算性质、指数函数的图像与性质、对数定义及运算法则、对数函数的图像与性质、指数函数与对数函数的实际应用等内容,感悟数学与现实的关联,把握事物的本质,形成理性思考问题的品质和精神. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 目标 --> |
| | | <div class="page-box" page="121"> |
| | | <div v-if="showPageList.indexOf(121) > -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.实数指数幂.</p> |
| | | <p> |
| | | 能体会指数从正整数推广到有理数、实数的过程,了解实数指数幂的运算法则. |
| | | </p> |
| | | <p>2.指数函数和对数函数.</p> |
| | | <p>能借助几何直观和代数运算认识指数函数和对数函数;</p> |
| | | <p> |
| | | 了解指数函数和对数函数的定义,理解它们的图像及性质,感悟数形结合的数学思想; |
| | | </p> |
| | | <p>会用对数的定义进行指数式与对数式的互化;</p> |
| | | <p>了解对数的性质和运算法则.</p> |
| | | <p>3.指数函数与对数函数的实际应用.</p> |
| | | <p>能从实际情境抽象出指数函数、对数函数模型解决简单问题.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | |
| | | <!-- 115 --> |
| | | <div class="page-box" page="122"> |
| | | <div v-if="showPageList.indexOf(122) > -1"> |
| | | |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>115</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h2 id="b022"> |
| | | 4.1 实数指数幂<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <h3 id="c034"> |
| | | 4.1.1 有理数指数幂<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"> |
| | | 如果<i>b</i><sup>2</sup>=<i>a</i>,那么<i>b</i>就叫作<i>a</i> |
| | | 的平方根(或二次方根).因为<i>b</i><sup>2</sup>≥0,故当<i>a</i><0时,在实数范围内<i>a</i>没有平方根;当<i>a</i>>0时,<i>a</i>的平方根有两个,它们互为相反数,分别为<math |
| | | display="0"> |
| | | <msqrt> |
| | | <mi>a</mi> |
| | | </msqrt> |
| | | </math>和<math display="0"> |
| | | <mo>−</mo> |
| | | <msqrt> |
| | | <mi>a</mi> |
| | | </msqrt> |
| | | </math>;当<i>a</i>=0时, |
| | | <math display="0"> |
| | | <msqrt> |
| | | <mn>0</mn> |
| | | </msqrt> |
| | | <mo>=</mo> |
| | | <mn>0</mn> |
| | | </math>.例如, ±3就是9的平方根. |
| | | </p> |
| | | <p class="block"> |
| | | 如果<i>b</i><sup>3</sup>=<i>a</i>,那么<i>b</i>就叫作<i>a</i>的立方根(或三次方根).在实数范围内<i>a</i>只有一个立方根,记为<math |
| | | display="0"> |
| | | <mroot> |
| | | <mi>a</mi> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | </math>.例如,2就是8的立方根. |
| | | </p> |
| | | </div> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 一般地,如果<i>b<sup>n</sup></i>=<i>a</i>(<i>n</i>>1,<i>n</i>∈<b>N</b>),那么<i>b</i>就叫作<i>a</i>的<i>n</i>次方根. |
| | | </p> |
| | | <p> |
| | | 当<i>n</i>是奇数时,正数<i>a</i>的<i>n</i>次方根是一个正数,负数<i>a</i>的<i>n</i>次方根是一个负数.这时,<i>a</i>的<i>n</i>次方根用符号<math |
| | | display="0"> |
| | | <mroot> |
| | | <mi>a</mi> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | </math>表示.例如, |
| | | </p> |
| | | <math display="block"> |
| | | <mroot> |
| | | <mn>128</mn> |
| | | <mn>7</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <mo>,</mo> |
| | | <mroot> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>128</mn> |
| | | </mrow> |
| | | <mn>7</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | <mo>,</mo> |
| | | <mroot> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>6</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p> |
| | | 当<i>n</i>是偶数时,正数<i>a</i>的<i>n</i>次方根有两个,两数互为相反数.这时,正数<i>a</i>的正的<i>n</i>次方根用符号<math display="0"> |
| | | <mroot> |
| | | <mi>a</mi> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | </math>表示,负的<i>n</i>次方根用符号<math display="0"> |
| | | <mo>−</mo> |
| | | <mroot> |
| | | <mi>a</mi> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | </math>表示.正的<i>n</i>次方根与负的<i>n</i>次方根可以合并写成<math display="0"> |
| | | <mo>±</mo> |
| | | <mroot> |
| | | <mi>a</mi> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>.例如, |
| | | </p> |
| | | <math display="block"> |
| | | <mroot> |
| | | <mn>64</mn> |
| | | <mn>6</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <mo>,</mo> |
| | | <mo>−</mo> |
| | | <mroot> |
| | | <mn>64</mn> |
| | | <mn>6</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | <mo>,</mo> |
| | | <mo>±</mo> |
| | | <mroot> |
| | | <mn>64</mn> |
| | | <mn>6</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mo>±</mo> |
| | | <mn>2.</mn> |
| | | </math> |
| | | <p>负数没有偶次方根.</p> |
| | | <p> |
| | | 0的任何次方根都是0,记作 |
| | | <math display="0"> |
| | | <mroot> |
| | | <mn>0</mn> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mn>0</mn> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 形如 |
| | | <math display="0"> |
| | | <mroot> |
| | | <mi>a</mi> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>n</mi> |
| | | <mo>></mo> |
| | | <mn>1</mn> |
| | | </math>(<i>n</i>>1,<i>n</i>∈<b>N</b><sub>+</sub>)的式子叫作<b>根式</b>,<i>n</i>叫作<b>根指数</b>,<i>a</i>叫作<b>被开方数</b>. |
| | | </p> |
| | | <p>根据<i>n</i>次方根的定义,根式具有下列性质.</p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mroot> |
| | | <mi>a</mi> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mi>a</mi> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | (2) 当<i>n</i>为奇数时,<math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mi>a</mi> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | 当<i>n</i>为偶数时,<math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mrow> |
| | | <mo stretchy="false">|</mo> |
| | | </mrow> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo stretchy="false">|</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">{</mo> |
| | | <mtable columnalign="left left" columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mi>a</mi> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd> |
| | | <mi>a</mi> |
| | | <mo>⩾</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>−</mo> |
| | | <mi>a</mi> |
| | | <mo>,</mo> |
| | | </mtd> |
| | | <mtd> |
| | | <mi>a</mi> |
| | | <mo>.</mo> |
| | | <mo><</mo> |
| | | <mn>0</mn> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | <mo data-mjx-texclass="CLOSE" fence="true" stretchy="true" symmetric="true"></mo> |
| | | </mrow> |
| | | </math>. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 116 --> |
| | | <div class="page-box" page="123"> |
| | | <div v-if="showPageList.indexOf(123) > -1"> |
| | | |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>116</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 计算. |
| | | </p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | </math>;(2) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mn>5</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | </math>;(3) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mn>7</mn> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | (4) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mn>7</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | </math>;(5) 81的4次方根. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1)<math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mn>5</mn> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | (2) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mn>5</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mn>5</mn> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | (3) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>7</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mn>7</mn> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | (4) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mn>7</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">|</mo> |
| | | <mo>−</mo> |
| | | <mn>7</mn> |
| | | <mo data-mjx-texclass="CLOSE">|</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mn>7</mn> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | (5) 因为(±3)<sup>4</sup>=81,所以81的4次方根是±3,即<math display="0"> |
| | | <mo>±</mo> |
| | | <mroot> |
| | | <mn>81</mn> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mo>±</mo> |
| | | <mn>3</mn> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 化简. |
| | | </p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <mi>a</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | </math>;(2) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <mrow> |
| | | <mi>π</mi> |
| | | </mrow> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <mi>a</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <mi>a</mi> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | (2) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <mrow> |
| | | <mi>π</mi> |
| | | </mrow> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">|</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <mrow> |
| | | <mi>π</mi> |
| | | </mrow> |
| | | <mo data-mjx-texclass="CLOSE">|</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>3</mn> |
| | | <mo>−</mo> |
| | | <mrow> |
| | | <mi>π</mi> |
| | | </mrow> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mrow> |
| | | <mi>π</mi> |
| | | </mrow> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </math>. |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 在初中,我们曾学习过整数幂的相关知识.<i>a<sup>n</sup></i>(<i>n</i>∈<b>N</b><sub>+</sub>)称为<i>a</i>的<i>n</i>次幂,<i>a</i>叫作底数,<i>n</i>叫作指数. |
| | | </p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <munder> |
| | | <mrow data-mjx-texclass="OP"> |
| | | <munder> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>⋅</mo> |
| | | <mi>a</mi> |
| | | <mo>⋅</mo> |
| | | <mi>a</mi> |
| | | <mo>⋅</mo> |
| | | <mo>⋯</mo> |
| | | <mo>⋅</mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | <mo>⏟</mo> |
| | | </munder> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | <mo stretchy="false">↑</mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </munder> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>n</mi> |
| | | <mo>∈</mo> |
| | | <msub> |
| | | <mrow> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>+</mo> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>; |
| | | </p> |
| | | <p>(2) <i>a</i><sup>0</sup>=1(<i>a</i>≠0);</p> |
| | | <p> |
| | | (3) |
| | | <math display="0"> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>a</mi> |
| | | <mo>≠</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mi>n</mi> |
| | | <mo>∈</mo> |
| | | <msub> |
| | | <mrow> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>+</mo> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>. |
| | | </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">分数指数幂</p> |
| | | </div> |
| | | <p>试想,如果幂指数<i>n</i>是分数时,此时的指数幂应该如何表示呢?</p> |
| | | <p> |
| | | 为此,我们现将整数指数幂的概念进行推广,利用刚学习过的根式来表示分数指数幂,规定<b>分数指数幂</b>的意义如下(为简化讨论,我们约定底数<i>a</i>>0). |
| | | </p> |
| | | <math display="block"> |
| | | <mtable columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mi>m</mi> |
| | | <mi>n</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mroot> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>m</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mi>m</mi> |
| | | <mo>,</mo> |
| | | <mi>n</mi> |
| | | <mo>∈</mo> |
| | | <msub> |
| | | <mrow> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>+</mo> |
| | | </mrow> |
| | | </msub> |
| | | <mo>,</mo> |
| | | <mi>n</mi> |
| | | <mo>></mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>,</mo> |
| | | <mi>m</mi> |
| | | <mo>=</mo> |
| | | <mn>1</mn> |
| | | <mtext> 时, 有 </mtext> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mi>n</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mroot> |
| | | <mi>a</mi> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mo>.</mo> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mi>m</mi> |
| | | <mi>n</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mi>m</mi> |
| | | <mi>n</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mroot> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>m</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | </mfrac> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mi>m</mi> |
| | | <mo>,</mo> |
| | | <mi>n</mi> |
| | | <mo>∈</mo> |
| | | <msub> |
| | | <mrow> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>+</mo> |
| | | </mrow> |
| | | </msub> |
| | | <mo>,</mo> |
| | | <mi>n</mi> |
| | | <mo>></mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>.</mo> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | </math> |
| | | <p> |
| | | 这样,幂指数的概念就从整数指数幂推广到了有理数指数幂.只要每一个有理数指数幂有意义,整数指数幂的运算性质对有理数指数幂就同样适用.因此,我们初中 |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 117 --> |
| | | <div class="page-box" page="124"> |
| | | <div v-if="showPageList.indexOf(124) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>117</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="t0"> |
| | | 学习过的整数指数幂的运算性质就可以推广到有理数指数幂. |
| | | </p> |
| | | <p>设<i>a</i>>0,<i>b</i>>0,<i>m</i>,<i>n</i>∈<b>Q</b>,则</p> |
| | | <p> |
| | | (1) <i>a<sup>m</sup> a<sup>n</sup></i>=<i>a<sup>m+n</sup></i>; |
| | | </p> |
| | | <p> |
| | | (2)(<i>a<sup>m</sup></i>)<i><sup>n</sup></i>=<i>a<sup>mn</sup></i>; |
| | | </p> |
| | | <p> |
| | | (3)(<i>ab</i>)<i><sup>n</sup></i>=<i>a<sup>n</sup> b<sup>n</sup></i>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例3</b></span> 将下列根式用分数指数幂表示(式中字母均为正实数). |
| | | </p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | </math>;(2) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>6</mn> |
| | | </mroot> |
| | | </math>;(3) |
| | | <math display="0"> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mroot> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | (2) |
| | | <math display="0"> |
| | | <mroot> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>6</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>6</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </math>;(注意:此处不能化简为<math display="0"> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </math>) |
| | | </p> |
| | | <p> |
| | | (3) |
| | | <math display="0"> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mroot> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </math> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例4</b></span> 化简(式中字母均为正实数). |
| | | </p> |
| | | <p> |
| | | (1)<math display="0"> |
| | | <msup> |
| | | <mn>27</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </math>;(2) |
| | | <math display="0"> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </msup> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1)<math display="0"> |
| | | <msup> |
| | | <mn>27</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msup> |
| | | <mn>27</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mroot> |
| | | <mn>27</mn> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | (2)<math display="0"> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>6</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>6</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[124]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 118 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c035">4.1.2 实数指数幂<span class="fontsz2">>>></span></h3> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/wttc.jpg" /> |
| | | </p> |
| | | <p> |
| | | 小学我们学习了自然数,初中从自然数拓展到整数、有理数乃至实数.类似地,在学习有理数指数幂的基础上,我们可以将<i>a<sup>x</sup></i>中指数<i>x</i>的取值范围从有理数拓展到全体实数,此时,<i>a<sup>x</sup></i>的意义是什么呢?如<math |
| | | display="0"> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <msqrt> |
| | | <mn>3</mn> |
| | | </msqrt> |
| | | </mrow> |
| | | </msup> |
| | | </math>,<math display="0"> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <msqrt> |
| | | <mn>2</mn> |
| | | </msqrt> |
| | | </mrow> |
| | | </msup> |
| | | </math>,它们是一个确定的数吗?能否计算出结果呢? |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /> |
| | | </p> |
| | | <p> |
| | | 实数指数幂 事实上,我们可以通过科学计算器计算出<math display="0"> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <msqrt> |
| | | <mn>3</mn> |
| | | </msqrt> |
| | | </mrow> |
| | | </msup> |
| | | </math>,<math display="0"> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <msqrt> |
| | | <mn>2</mn> |
| | | </msqrt> |
| | | </mrow> |
| | | </msup> |
| | | </math>的值(请同学们自己利用科学计算器或下载计算机软件进行计算).如果精确到0.01时,<math display="0"> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <msqrt> |
| | | <mn>3</mn> |
| | | </msqrt> |
| | | </mrow> |
| | | </msup> |
| | | </math>的近似值为3.32,<math display="0"> |
| | | <msup> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mrow> |
| | | <msqrt> |
| | | <mn>2</mn> |
| | | </msqrt> |
| | | </mrow> |
| | | </msup> |
| | | </math>的近似值为0.14,即表明这些无理数指数幂都是一个确定的实数.这样,我们将指数幂<i>a<sup>x</sup></i>(<i>a</i>>0)中指数<i>x</i>的取值范围从整数逐步拓展到有理数、无理数,乃至实数.当<i>x</i>为任意实数时,<b>实数指数幂</b><i>a<sup>x</sup></i>(<i>a</i>>0)表示一个确定实数.现实生活中,我们通过类比、联想、猜想等方式可创新设计出很多不同的事物和模式. |
| | | </p> |
| | | <p> |
| | | 有理数指数幂的运算性质同样适用于实数指数幂的运算性质(证明略),即当<i>a</i>>0,<i>b</i>>0,<i>p</i>,<i>q</i>∈<b>R</b>时,有 |
| | | </p> |
| | | <p> |
| | | (1) <i>a<sup>p</sup> a<sup>q</sup></i>=<i>a<sup>p+q</sup></i>; |
| | | </p> |
| | | <p> |
| | | (2)(<i>a<sup>p</sup></i>)<i><sup>q</sup></i>=<i>a<sup>pq</sup></i>; |
| | | </p> |
| | | <p> |
| | | (3)(<i>ab</i>)<i><sup>p</sup></i>=<i>a<sup>p</sup> b<sup>p</sup></i>. |
| | | </p> |
| | | <p>注意:运算性质成立的条件是每个实数指数幂都有意义.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 119 --> |
| | | <div class="page-box" page="126"> |
| | | <div v-if="showPageList.indexOf(126) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>119</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/tbts.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"> |
| | | 对例1(1) |
| | | 题,我们需要将某些底数变形为指数幂的形式,以方便利用实数指数幂的运算法则进行计算或者化简. |
| | | </p> |
| | | </div> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 计算(式中字母均为正实数). |
| | | </p> |
| | | <p> |
| | | (1)<math display="0"> |
| | | <msup> |
| | | <mn>16</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>−</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>27</mn> |
| | | </mfrac> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msqrt> |
| | | <mn>2</mn> |
| | | </msqrt> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msup> |
| | | </math>;(2) |
| | | <math display="0"> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>⋅</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>÷</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mtable columnalign="left" columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mtext>(1)</mtext> |
| | | <msup> |
| | | <mn>16</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>27</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <msqrt> |
| | | <mn>2</mn> |
| | | </msqrt> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <msup> |
| | | <mo stretchy="false">)</mo> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">[</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">]</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | <mo>×</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>−</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | <mo>×</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | <mo>=</mo> |
| | | <mn>0</mn> |
| | | <mo>;</mo> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mtext>(2)</mtext> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>⋅</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>÷</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | <mo>×</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | <mo>×</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mo>×</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>÷</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | <mo>×</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>×</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>9</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | <mo>.</mo> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | </math> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 化简(式中字母均为正实数). |
| | | </p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <msqrt> |
| | | <mn>2</mn> |
| | | </msqrt> |
| | | <mo>×</mo> |
| | | <mroot> |
| | | <mn>8</mn> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | <mo>×</mo> |
| | | <mroot> |
| | | <mn>64</mn> |
| | | <mn>8</mn> |
| | | </mroot> |
| | | </math>;(2) |
| | | <math display="0"> |
| | | <msqrt> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | </msqrt> |
| | | <mo>·</mo> |
| | | <mroot> |
| | | <mrow> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>·</mo> |
| | | <mroot> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mn>6</mn> |
| | | </mroot> |
| | | </math>. |
| | | </p> |
| | | <p class="block"> |
| | | <span class="zt-ls2"><b>分析</b></span> 运算思路是将根式转化为分数指数幂,然后再化简运算. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | </p> |
| | | <math display=""> |
| | | <mtable columnalign="left" columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <mo stretchy="false">(1)</mo> |
| | | <msqrt> |
| | | <mn>2</mn> |
| | | </msqrt> |
| | | <mo>×</mo> |
| | | <mroot> |
| | | <mn>8</mn> |
| | | <mn>4</mn> |
| | | </mroot> |
| | | <mo>×</mo> |
| | | <mroot> |
| | | <mn>64</mn> |
| | | <mn>8</mn> |
| | | </mroot> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>×</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>×</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>6</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>8</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>×</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>×</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>6</mn> |
| | | <mn>8</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>6</mn> |
| | | <mn>8</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mn>4</mn> |
| | | <mo>;</mo> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mtext>(2)</mtext> |
| | | <msqrt> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | </msqrt> |
| | | <mo>⋅</mo> |
| | | <mroot> |
| | | <mrow> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>⋅</mo> |
| | | <mroot> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mn>6</mn> |
| | | </mroot> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>⋅</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>⋅</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>a</mi> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>6</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>⋅</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>⋅</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>6</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>6</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>6</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>⋅</mo> |
| | | <msup> |
| | | <mi>b</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>+</mo> |
| | | <mfrac> |
| | | <mn>5</mn> |
| | | <mn>6</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mi>a</mi> |
| | | <mo>.</mo> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | </math> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 120 --> |
| | | <div class="page-box" page="127"> |
| | | <div v-if="showPageList.indexOf(127) > -1"> |
| | | |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>120</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | <span class="zt-ls"><b>例3</b></span> 计算 |
| | | 2<sup>0</sup>+2<sup>1</sup>+2<sup>2</sup>+2<sup>3</sup>+…+2<i><sup>x</sup></i>(<i>x</i>∈<b>N</b>). |
| | | </p> |
| | | <p class="block"> |
| | | <span |
| | | class="zt-ls2"><b>分析</b></span> 观察这个式子的特点,每一项都是前面一项的2倍(除第1项外);运算思路可考虑将代数式每项乘2后再与原式相减.数学上把这种运算方法叫作“错位相减”. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 令 |
| | | </p> |
| | | <math display="block"> |
| | | <mi>S</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>0</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <mo>…</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p class="right">①</p> |
| | | <p>将①式两边同时乘2,得</p> |
| | | <math display="block"> |
| | | <mn>2</mn> |
| | | <mi>S</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <mo>…</mo> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p class="right">②</p> |
| | | <p>用②式减①式可得</p> |
| | | <p> |
| | | 2<i>S</i>-<i>S</i>=(2<sup>1</sup>+2<sup>2</sup>+2<sup>3</sup>+…+2<i><sup>x</sup></i>+2<i><sup>x</sup></i><sup>+1</sup>)-(2<sup>0</sup>+2<sup>1</sup>+2<sup>2</sup>+2<sup>3</sup>+…+2<i><sup>x</sup></i><sup>-1</sup>+2<i><sup>x</sup></i>), |
| | | </p> |
| | | <p> |
| | | 即<i>S</i>=2<i><sup>x+1</sup></i>-1, |
| | | </p> |
| | | <p> |
| | | 所以, 2<sup>0</sup>+2<sup>1</sup>+2<sup>2</sup>+2<sup>3</sup>+…+2<i><sup>x</sup></i>=2<i><sup>x+1</sup></i>-1. |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[127]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 121 --> |
| | | <div class="page-box" page="128"> |
| | | <div v-if="showPageList.indexOf(128) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>121</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c036">习题4.1<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[128]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <h2 id="b023"> |
| | | 4.2 指数函数<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <h3 id="c037"> |
| | | 4.2.1 指数函数的定义与图像<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/gcsk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 情境1:《庄子·天下篇》中有一段脍炙人口的话:“一尺之棰,日取其半,万世不竭.”这里的“一尺之棰”,即一尺(长度单位,1尺约合0.33 |
| | | m)长的木棍,“日取其半”即每天取它的一半.若一直“日取其半”,则每天剩下的木棍长度就是下面的一列数字. |
| | | </p> |
| | | <math display="block"> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo>,</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>,</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>,</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>4</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>,</mo> |
| | | <mo>⋯</mo> |
| | | </math> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 122 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | 记取到第<i>x</i>天时剩下的长度为<i>y</i>,那么<i>y</i>与 |
| | | <i>x</i>的函数关系是 |
| | | </p> |
| | | <math display="block"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p class="right">①</p> |
| | | <p> |
| | | 其中指数<i>x</i>是自变量,定义域是<i>x</i>∈<b>N</b><sub>+</sub>. |
| | | </p> |
| | | <p> |
| | | 情境2:细胞每分裂1次其数量变为原来的两倍,则每次分裂后的细胞数量见表4-1. |
| | | </p> |
| | | <p class="img">表4-1</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0133-2.jpg" /> |
| | | </p> |
| | | <p> |
| | | 如果设细胞分裂的次数为<i>x</i>,对应分裂后的细胞数量为<i>y</i>,那么<i>y</i>与<i>x</i>的函数关系是 |
| | | </p> |
| | | <math display="block"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>2</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p class="right">②</p> |
| | | <p> |
| | | 其中指数<i>x</i>是自变量,定义域是<i>x</i>∈<b>N</b><sub>+</sub>. |
| | | </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">指数函数</p> |
| | | </div> |
| | | <p> |
| | | 如果用字母<i>a</i>代替上述①②两式中的底数<math display="0"> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </math>和2,那么函数<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>和 <i>y</i>=2<i><sup>x</sup></i>就可以表示为 |
| | | </p> |
| | | <p class="center"> |
| | | <i>y</i>=<i>a<sup>x</sup></i> |
| | | </p> |
| | | <p> |
| | | 的形式,其中指数<i>x</i>是自变量,底数<i>a</i>是一个大于0且不等于 |
| | | 1的常量. |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 一般地,形如<i>y</i>=<i>a<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1)的函数叫作<b>指数函数</b>,其中指数<i>x</i>是自变量,定义域是<b>R</b>. |
| | | </p> |
| | | <p> |
| | | <b>例</b> 已知指数函数<i>f</i>(<i>x</i>)=<i>a<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1),且<i>f</i>(3)=125. |
| | | </p> |
| | | <p>(1) 求函数<i>f</i>(<i>x</i>)的解析式;</p> |
| | | <p> |
| | | (2) 求<i>f</i>(0),<i>f</i>(2),<i>f</i>(-2),<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>的值. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) |
| | | 因为<i>f</i>(<i>x</i>)=<i>a<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1),且<i>f</i>(3)=125,所以<i>a</i><sup>3</sup>=125,解得<i>a</i>=5,于是<i>f</i>(<i>x</i>)=5<i><sup>x</sup></i>. |
| | | </p> |
| | | <p> |
| | | (2) |
| | | <i>f</i>(0)=5<sup>0</sup>=1,<i>f</i>(2)=5<sup>2</sup>=25,<math display="0"> |
| | | <mi>f</mi> |
| | | <mo>−</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>25</mn> |
| | | </mfrac> |
| | | </math>,<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msqrt> |
| | | <mn>5</mn> |
| | | </msqrt> |
| | | </math>. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 123 --> |
| | | <div class="page-box" page="130"> |
| | | <div v-if="showPageList.indexOf(130) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>123</span></p> |
| | | </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[130]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/zshg.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"> |
| | | 初中我们学习了正比例函数、反比例函数和二次函数,通过描点法画出它们的图像分别是直线、双曲线和抛物线(如图4-1所示).我们可类比借鉴学习上述函数的经验,画出指数函数的图像,再利用图像与解析式,研究其单调性、奇偶性等. |
| | | </p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0134-3.jpg" /> |
| | | </p> |
| | | <p class="img">图4-1</p> |
| | | </div> |
| | | <p><b>类比归纳</b></p> |
| | | <p> |
| | | 与初中画二次函数图像一样,也可用描点法画出指数函数的图像.下面我们以<i>y</i>=2<i><sup>x</sup></i>和<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>为例,画出其函数图像. |
| | | </p> |
| | | <p>第一步:列表(如表4-2所示).</p> |
| | | <p class="img">表4-2</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0134-5.jpg" /> |
| | | </p> |
| | | <p> |
| | | 第二步:描点,并且用光滑的曲线连接所描的点,画出它们的图像(如图4-2所示). |
| | | </p> |
| | | <p> |
| | | 利用相同方法,我们还可以在同一平面直角坐标系中画出<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>, |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 124 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>, <i>y</i>=2.3<i><sup>x</sup></i>,<i>y</i>=3<i><sup>x</sup></i>的图像,如图4-3所示. |
| | | <ul class="fl"> |
| | | <li style="margin-top: 30px"> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0135-2.jpg" /> |
| | | </p> |
| | | <p class="img">图4-2</p> |
| | | </li> |
| | | <li> |
| | | <p class="center"> |
| | | <img class="img-b" alt="" src="../../assets/images/0135-3.jpg" /> |
| | | </p> |
| | | <p class="img">图4-3</p> |
| | | </li> |
| | | </ul> |
| | | <h3 id="c038"> |
| | | 4.2.2 指数函数的性质<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/gcsk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 观察指数函数的图像,描述这些图像在位置、公共点和变化趋势等方面的共性特征. |
| | | </p> |
| | | <p> |
| | | (1) 图中所有指数函数图像均在<i>x</i>轴的上方(<b>位置特征</b>); |
| | | </p> |
| | | <p> |
| | | (2) 图中所有指数函数图像都经过定点(0,1)(<b>公共点特征</b>); |
| | | </p> |
| | | <p> |
| | | (3) |
| | | 在定义域内,指数函数<i>y</i>=2<i><sup>x</sup></i>,<i>y</i>=2.3<i><sup>x</sup></i>,<i>y</i>=3<i><sup>x</sup></i>图像从左向右分别逐渐上升,在第二象限内向左与<i>x</i>轴无限接近;指数函数<math |
| | | display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>,<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>,<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>图像从左向右分别逐渐下降,在第一象限内向右与<i>x</i>轴无限接近(<b>变化趋势特征</b>). |
| | | </p> |
| | | <p> |
| | | 我们观察分析发现,指数函数<i>y</i>=<i>a<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1)的图像按底数<i>a</i>的取值,可分为0<<i>a</i><1和<i>a</i>>1两种类型. |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 一般地,指数函数<i>y</i>=<i>a<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1)具有下列性质. |
| | | </p> |
| | | <p>(1) 函数的定义域为<i>R</i>,值域为(0,+∞);</p> |
| | | <p>(2) 当<i>x</i>=0时,函数值<i>y</i>=1;</p> |
| | | <p> |
| | | (3) |
| | | 当<i>a</i>>1时,函数在(-∞,+∞)内是增函数;当0<<i>a</i><1时,函数在(-∞,+∞)内是减函数. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 125 --> |
| | | <div class="page-box" page="132"> |
| | | <div v-if="showPageList.indexOf(132) > -1"> |
| | | |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>125</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | 指数函数<i>y</i>=<i>a<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1)的图像和性质可以总结如表4-3所示. |
| | | </p> |
| | | <p class="img">表4-3</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0136-1.jpg" /> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 判断下列函数哪些是指数函数,并画出函数图像验证. |
| | | </p> |
| | | <p> |
| | | (1) <i>y</i>=0.5<i><sup>x</sup></i>;(2) <i>y</i>=2×3<i><sup>x</sup></i>;(3) <i>y</i>=<i>x</i><sup>2</sup>. |
| | | </p> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/tbts.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"> |
| | | 函数<i>y</i>=2×3<i><sup>x</sup></i> |
| | | </p> |
| | | <p class="block"> |
| | | 在形式上与指数函数相似,但不符合指数函数的定义,我们从其函数图像可以看到没有过定点(0,1). |
| | | </p> |
| | | </div> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 依据指数函数<i>y</i>=<i>a<sup>x</sup></i>的定义,<i>y</i>=0.5<i><sup>x</sup></i>是指数函数,<i>y</i>=2×3<i><sup>x</sup></i>和<i>y</i>=<i>x</i><sup>2</sup>不是指数函数.画出函数图像(如图4-4所示),函数<i>y</i>=0.5<i><sup>x</sup></i>的图像符合指数函数图像的特征;函数<i>y</i>=2×3<i><sup>x</sup></i>的图像虽与指数函数图像很相似,但并没有过定点(0,1);函数<i>y</i>=<i>x</i><sup>2</sup>的图像是二次函数的图像. |
| | | </p> |
| | | <p class="center"> |
| | | <img class="img-b" alt="" src="../../assets/images/0136-2.jpg" /> |
| | | </p> |
| | | <p class="img">图4-4</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[131]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 126 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 判断下列函数在(-∞,+∞)内的单调性. |
| | | </p> |
| | | <p> |
| | | (1) <i>y</i>=4<i><sup>x</sup></i>;(2) <i>y</i>=3<i><sup>-x</sup></i>;(3) |
| | | <math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mi>x</mi> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 因为4>1 , 所以<i>y</i>=4<i><sup>x</sup></i>在(-∞,+∞)内是增函数(如图4-5所示). |
| | | </p> |
| | | <p> |
| | | (2) |
| | | <math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>,因为<math display="0"> |
| | | <mn>0</mn> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo><</mo> |
| | | <mn>1</mn> |
| | | </math>,所以<i>y</i>=3<i><sup>-x</sup></i>在(-∞,+∞)内是减函数(如图4-6所示). |
| | | </p> |
| | | <p> |
| | | (3)<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mi>x</mi> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mroot> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <msup> |
| | | <mo stretchy="false">)</mo> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | </math>,因为<math display="0"> |
| | | <mroot> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>></mo> |
| | | <mn>1</mn> |
| | | </math>,所以<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mi>x</mi> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | </math>在(-∞,+∞)内是增函数(如图4-7所示). |
| | | </p> |
| | | <ul class="fl"> |
| | | <li> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0137-7.jpg" /> |
| | | </p> |
| | | <p class="img">图4-5</p> |
| | | </li> |
| | | <li> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0137-8.jpg" /> |
| | | </p> |
| | | <p class="img">图4-6</p> |
| | | </li> |
| | | <li> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0137-9.jpg" /> |
| | | </p> |
| | | <p class="img">图4-7</p> |
| | | </li> |
| | | </ul> |
| | | <p> |
| | | <span class="zt-ls"><b>例3</b></span> 比较下列各题中两个值的大小. |
| | | </p> |
| | | <p> |
| | | (1) 1.8<sup>2.5</sup>与1.8<sup>3</sup>;(2) |
| | | 0.9<sup>-0.2</sup>与0.9<sup>-0.3</sup>. |
| | | </p> |
| | | <p class="block"> |
| | | <span |
| | | class="zt-ls2"><b>分析</b></span> 1.8<sup>2.5</sup>和1.8<sup>3</sup>分别可以看作<i>y</i>=1.8<i><sup>x</sup></i>在<i>x</i>=2.5和<i>x</i>=3处的函数值,这样就可以利用函数的单调性来比较函数值的大小.0.9<sup>-0.2</sup>和0.9<sup>-0.3</sup>分别可以看作<i>y</i>=0.9<i><sup>x</sup></i>在<i>x</i>=-0.2和<i>x</i>=-0.3处的函数值,同样可以利用函数的单调性来比较函数值的大小. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 因为<i>y</i>=1.8<i><sup>x</sup></i>是<b>R</b>上的增函数,且2.5<3,所以 |
| | | </p> |
| | | <p class="center">1.8<sup>2.5</sup><1.8<sup>3</sup>.</p> |
| | | <p> |
| | | (2) 因为<i>y</i>=0.9<i><sup>x</sup></i>是<b>R</b>上的减函数,且-0.2>-0.3,所以 |
| | | </p> |
| | | <p class="center">0.9<sup>-0.2</sup><0.9<sup>-0.3</sup>.</p> |
| | | <p> |
| | | <span class="zt-ls"><b>例4</b></span> 求函数<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msqrt> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mi>x</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>−</mo> |
| | | <mn>4</mn> |
| | | </msqrt> |
| | | </math>的定义域. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | 要使函数有意义,必须满足2<i><sup>x</sup></i>-4≥0,即2<i><sup>x</sup></i>≥4,又因为<i>y</i>=2<i><sup>x</sup></i>是增函数,所以<i>x</i>≥2. |
| | | </p> |
| | | <p>故函数的定义域为2,+∞).</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 127 --> |
| | | <div class="page-box" page="134"> |
| | | <div v-if="showPageList.indexOf(134) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | </li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | <span |
| | | class="zt-ls"><b>例5</b></span> 已知指数函数<i>f</i>(<i>x</i>)=<i>a<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1)的图像过点(3,27). |
| | | </p> |
| | | <p> |
| | | (1) 求<i>f</i>(-1) 的值;(2) |
| | | 若<i>f</i>(m)≥9,求<i>m</i>的取值范围. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 图像过点(3,27),即<i>x</i>=3时,<i>f</i>(3)=27. |
| | | </p> |
| | | <p> |
| | | 由27=<i>a</i><sup>3</sup>,得<i>a</i>=3, 即<i>f</i>(<i>x</i>)=3<i><sup>x</sup></i>. |
| | | </p> |
| | | <p> |
| | | 所以<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 因为<i>f</i>(<i>m</i>)=3<i><sup>m</sup></i>,所以得到3<i><sup>m</sup></i>≥9,即3<i><sup>m</sup></i>≥3<sup>2</sup>. |
| | | </p> |
| | | <p> |
| | | 函数<i>y</i>=3<i><sup>x</sup></i>在定义域内是增函数. |
| | | </p> |
| | | <p>因此,<i>m</i>≥2,即<i>m</i>的取值范围为[2,+∞).</p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[134]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c039">习题4.2<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[135]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 129 --> |
| | | <div class="page-box" page="136"> |
| | | <div v-if="showPageList.indexOf(136) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>129</span></p> |
| | | </li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h2 id="b024"> |
| | | 4.3 对数<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <h3 id="c040">4.3.1 对数的定义<span class="fontsz2">>>></span></h3> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/wttc.jpg" /> |
| | | </p> |
| | | <p> |
| | | 在上一节“观察思考”的情境1中,我们提到了《庄子·天下篇》中的“一尺之棰,日取其半,万世不竭”.现已知“一尺之棰”剩下八分之一尺,请问过去了几天?如果是剩下<i>N</i>尺呢? |
| | | </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">对数</p> |
| | | <p class="block">底数</p> |
| | | <p class="block">真数</p> |
| | | <p class="block">指数式</p> |
| | | <p class="block">对数式</p> |
| | | <p class="block">常用对数</p> |
| | | <p class="block">自然对数</p> |
| | | </div> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 一般地,如果<i>a<sup>x</sup></i>=<i>N</i>(<i>a</i>>0,且<i>a</i>≠1),那么数<i>x</i>叫作以<i>a</i>为底<i>N</i>的<b>对数</b>,记作 |
| | | </p> |
| | | <p class="center"><i>x</i>=log<sub>a</sub><i>N</i>.</p> |
| | | <p> |
| | | 其中<i>a</i>叫作对数的<b>底数</b>(简称底),<i>N</i>叫作<b>真数</b>. |
| | | </p> |
| | | <p> |
| | | 例如,2<sup>3</sup>=8,所以3就是以2为底8的对数,记作3=log |
| | | <sub>2</sub>8;再如,2<i><sup>x</sup></i>=<i>N</i>,所以<i>x</i>是以2为底<i>N</i>的对数,记作<i>x</i>=log |
| | | <sub>2</sub><i>N</i>. |
| | | </p> |
| | | <p> |
| | | 式子<i>a<sup>b</sup></i>=<i>N</i>叫作<b>指数式</b>,log |
| | | <i><sub>a</sub>N</i>=<i>b</i>叫作<b>对数式</b>.它们的关系如下. |
| | | </p> |
| | | <p class="center"> |
| | | <img class="img-c" alt="" src="../../assets/images/0140-3.jpg" /> |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | 通常,我们把以10为底的对数叫作<b>常用对数</b>,<i>N</i>的常用对数log |
| | | <sub>10</sub><i>N</i>简记作lg<i>N</i>.例如,log<sub>10</sub>5简记作lg5. |
| | | </p> |
| | | <p> |
| | | 另外,在科技、经济以及社会生活中经常使用无理数e,它的值为2.718 |
| | | 28…,以e为底的对数叫作<b>自然对数</b>.<i>N</i>的自然对数log |
| | | <sub>e</sub><i>N</i>简记作ln<i>N</i>.例如,log<sub>e</sub>8简记作ln8. |
| | | </p> |
| | | <p>根据对数的定义,对数有以下性质.</p> |
| | | <p>(1) 零和负数没有对数;</p> |
| | | <p> |
| | | (2) log<i><sub>a</sub></i>1=0,即1的对数为0; |
| | | </p> |
| | | <p> |
| | | (3) log<i><sub>a</sub>a</i>=1,即底数的对数为1. |
| | | </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[137]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 把下列指数式写成对数式. |
| | | </p> |
| | | <p> |
| | | (1) 5<sup>4</sup>=625;(2) |
| | | <math display="0"> |
| | | <msup> |
| | | <mn>8</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mn>16</mn> |
| | | </math>;(3) 10<sup>-2</sup>=0.01. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) log<sub>5</sub>625=4;(2) |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mn>16</mn> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </math>;(3) lg0.01=-2. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 把下列对数式写成指数式. |
| | | </p> |
| | | <p> |
| | | (1) log<sub>3</sub>243=5;(2) |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>27</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>3</mn> |
| | | </math>;(3) <i>ln</i>1=0. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 3<sup>5</sup>=243;(2) |
| | | <math display="0"> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>27</mn> |
| | | </mfrac> |
| | | </math>;(3) <i>e</i><sup>0</sup>=1. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例3</b></span> 求下列各式中<i>N</i>的值. |
| | | </p> |
| | | <p> |
| | | (1) lg<i>N</i>=-3;(2) |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mi mathvariant="bold">N</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 由lg<i>N</i>=-3,得<i>N</i>=10<sup>-3</sup>=0.001; |
| | | </p> |
| | | <p> |
| | | (2) 由<math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mi mathvariant="bold">N</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </math>,得<math display="0"> |
| | | <mi mathvariant="bold">N</mi> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>8</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mn>4</mn> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例4</b></span> 求下列各式中<i>x</i>的值. |
| | | </p> |
| | | <p> |
| | | (1) log <sub>2</sub>8=<i>x</i>;(2) log |
| | | <sub>4</sub>4<sup>5</sup>=<i>x</i>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 由log |
| | | <sub>2</sub>8=<i>x</i>,得2<i><sup>x</sup></i>=8,即2<i><sup>x</sup></i>=2<sup>3</sup>,所以<i>x</i>=3; |
| | | </p> |
| | | <p> |
| | | (2) 由log <sub>4</sub>4<sup>5</sup>=<i>x</i>,得4<i><sup>x</sup></i>=4<sup>5</sup>,所以<i>x</i>=5. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例5</b></span> 求下列各式的值. |
| | | </p> |
| | | <p> |
| | | (1) log<sub>5</sub>1;(2) log<sub>7</sub>7;(3) lg 10;(4) |
| | | ln e. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls2"><b>分析</b></span> 利用性质“1的对数为0”和“底数的对数为1” 直接得答案,不必转化成指 |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 131 --> |
| | | <div class="page-box" page="138"> |
| | | <div v-if="showPageList.indexOf(138) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>131</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p>数式.</p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) log<sub>5</sub>1=0;(2) log<sub>7</sub>7=1; |
| | | </p> |
| | | <p>(3) lg10=log<sub>10</sub>10=1;(4) ln e=log<sub>e</sub>e=1.</p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[138]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <h3 id="c041"> |
| | | 4.3.2 对数的运算性质<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/gcsk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 利用对数式与指数式的关系,填写表4-4,猜想对数的运算性质,并与同学交流. |
| | | </p> |
| | | <p class="img">表4-4</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0142-8.jpg" /> |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 132 --> |
| | | <div class="page-box" page="139"> |
| | | <div v-if="showPageList.indexOf(139) > -1"> |
| | | |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>132</li> |
| | | <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>我们可以得到两个正数的积、商、幂的对数运算性质.</p> |
| | | <p> |
| | | (1) |
| | | 积的对数:<b>两个正数积的对数,等于同一底数的这两个数的对数的和</b>,即 |
| | | </p> |
| | | <p class="center"> |
| | | log<i><sub>a</sub></i>(<i>MN</i>)=log<i><sub>a</sub>M</i>+log |
| | | <i><sub>a</sub>N</i>(<i>a</i>>0,且<i>a</i>≠1). |
| | | </p> |
| | | <p> |
| | | <b>证明</b> 设log<i><sub>a</sub>M</i>=<i>p</i>,log<i><sub>a</sub>N</i>=<i>q</i>, |
| | | </p> |
| | | <p> |
| | | 根据对数的定义,得<i>M</i>=<i>a<sup>p</sup></i>,<i>N</i>=<i>a<sup>q</sup></i>, |
| | | </p> |
| | | <p> |
| | | 所以 <i>MN</i>=<i>a<sup>p</sup> a<sup>q</sup></i>=<i>a<sup>p+q</sup></i>. |
| | | </p> |
| | | <p>把指数式化为对数式,得</p> |
| | | <p class="center"> |
| | | log<i><sub>a</sub></i>(<i>MN</i>)=<i>p</i>+<i>q</i>=log<i><sub>a</sub>M</i>+log<i><sub>a</sub>N</i>. |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 商的对数:<b>两个正数商的对数,等于同一底数的被除数的对数减去除数的对数,</b>即 |
| | | </p> |
| | | <math display="block"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <mi>M</mi> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>M</mi> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi mathvariant="bold">N</mi> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mtext>, 且 </mtext> |
| | | <mi>a</mi> |
| | | <mo>≠</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mtext>. </mtext> |
| | | </math> |
| | | <p> |
| | | (3) |
| | | 幂的对数:<b>一个正数幂的对数,等于幂指数乘这个数的对数,</b>即 |
| | | </p> |
| | | <p class="center"> |
| | | log<i><sub>a</sub>M<sup>q</sup></i>=<i>q</i>log |
| | | <i><sub>a</sub>M</i>(<i>a</i>>0,且<i>a</i>≠1,<i>q</i>∈<b>R</b>). |
| | | </p> |
| | | <p> |
| | | 特别地,log<i><sub>a</sub>a<sup>b</sup></i>=<i>b</i>(<i>a</i>>0,且<i>a</i>≠1). |
| | | </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[139]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <p> |
| | | <span |
| | | class="zt-ls"><b>例1</b></span> 用log<i><sub>a</sub>x</i>,log<i><sub>a</sub>y</i>,log<i><sub>a</sub>z</i>表示下列各式(式中字母均为正实数且<i>a</i>≠1). |
| | | </p> |
| | | <p> |
| | | (1) log<i><sub>a</sub></i>(<i>x</i><sup>2</sup><i>yz</i><sup>3</sup>);(2)<math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mrow> |
| | | <mi>y</mi> |
| | | <mi>z</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>;(3) |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <msqrt> |
| | | <mi>x</mi> |
| | | </msqrt> |
| | | <mrow> |
| | | <msup> |
| | | <mi>y</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mi>z</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p class="block"> |
| | | <span class="zt-ls2"><b>分析</b></span> 利用对数运算性质进行化简运算. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(1)</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mi>y</mi> |
| | | <msup> |
| | | <mi>z</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>y</mi> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mi>z</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>y</mi> |
| | | <mo>+</mo> |
| | | <mn>3</mn> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>z</mi> |
| | | <mo>;</mo> |
| | | </math> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(2)</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mrow> |
| | | <mi>y</mi> |
| | | <mi>z</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mi>x</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>y</mi> |
| | | <mi>z</mi> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>y</mi> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>z</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>y</mi> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>z</mi> |
| | | <mo>;</mo> |
| | | </math> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(3)</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <msqrt> |
| | | <mi>x</mi> |
| | | </msqrt> |
| | | <mrow> |
| | | <msup> |
| | | <mi>y</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mi>z</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msqrt> |
| | | <mi>x</mi> |
| | | </msqrt> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mi>y</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mi>z</mi> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | <mo>−</mo> |
| | | <mn>2</mn> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>y</mi> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>z</mi> |
| | | <mo>.</mo> |
| | | </math> |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 计算. |
| | | </p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mroot> |
| | | <mn>25</mn> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | </math>;(2) log <sub>3</sub>(9<sup>3</sup>×3<sup>5</sup>);(3) log |
| | | <sub>7</sub>56-log<sub>7</sub>8. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 133 --> |
| | | <div class="page-box" page="140"> |
| | | <div v-if="showPageList.indexOf(140) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | </li> |
| | | </ul> |
| | | |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(1)</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mroot> |
| | | <mn>25</mn> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mroot> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mn>3</mn> |
| | | </mroot> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>5</mn> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>5</mn> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | <mo>;</mo> |
| | | </math> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(2)</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mn>9</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>×</mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>9</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mn>6</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mn>6</mn> |
| | | <mo>+</mo> |
| | | <mn>5</mn> |
| | | <mo>=</mo> |
| | | <mn>11</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(3)</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>56</mn> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>8</mn> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <mn>56</mn> |
| | | <mn>8</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>7</mn> |
| | | <mo>=</mo> |
| | | <mn>1</mn> |
| | | <mo>.</mo> |
| | | </math> |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[140]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <h3 id="c042"> |
| | | 4.3.3(选学)换底公式、对数恒等式<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /> |
| | | </p> |
| | | <p> |
| | | 设log<i><sub>a</sub>N</i>=<i>x</i>,则<i>a<sup>x</sup></i>=<i>N</i>,两边取以<i>c</i>为底的对数,得log<i><sub>c</sub>a<sup>x</sup></i>=log<i><sub>c</sub>N</i>,于是<i>x</i>log<i><sub>c</sub>a</i>=log<i><sub>c</sub>N</i>,即<math |
| | | display="0"> |
| | | <mi>x</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>,所以<math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi mathvariant="bold">N</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p>于是,我们有<b>对数的换底公式:</b></p> |
| | | <math display="block"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mtext> 且 </mtext> |
| | | <mi>a</mi> |
| | | <mo>≠</mo> |
| | | <mn>1</mn> |
| | | <mo>;</mo> |
| | | <mi>c</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mtext>, 且 </mtext> |
| | | <mi>c</mi> |
| | | <mo>≠</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mtext>. </mtext> |
| | | </math> |
| | | <p>特别地,</p> |
| | | <math display="block"> |
| | | <mtable columnalign="left" columnspacing="1em" rowspacing="4pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mtext> 且 </mtext> |
| | | <mi>a</mi> |
| | | <mo>≠</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>;</mo> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>ln</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>ln</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mtext> 且 </mtext> |
| | | <mi>a</mi> |
| | | <mo>≠</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mo>.</mo> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | </math> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 求log<sub>27</sub>8·log <sub>32</sub>9的值. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | </p> |
| | | <math display="block"> |
| | | <mtable displaystyle="true" columnalign="right left right left right left right left right left right left" |
| | | columnspacing="0em 2em 0em 2em 0em 2em 0em 2em 0em 2em 0em" rowspacing="3pt"> |
| | | <mtr> |
| | | <mtd> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>27</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>8</mn> |
| | | <mo>⋅</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>32</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>9</mn> |
| | | </mtd> |
| | | <mtd> |
| | | <mi></mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>8</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>27</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>⋅</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>9</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>32</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>⋅</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | </mfrac> |
| | | </mtd> |
| | | </mtr> |
| | | <mtr> |
| | | <mtd></mtd> |
| | | <mtd> |
| | | <mi></mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>⋅</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | <mrow> |
| | | <mn>5</mn> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>2</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | <mo>.</mo> |
| | | </mtd> |
| | | </mtr> |
| | | </mtable> |
| | | </math> |
| | | <p> |
| | | <span |
| | | class="zt-ls"><b>例2</b></span> 求证:log<i><sub>a</sub>b</i>·log<i><sub>b</sub>c</i>·log<i><sub>c</sub>a</i>=1(<i>a</i>,<i>b</i>,<i>c</i>均为正实数,且均不等于1). |
| | | </p> |
| | | <p> |
| | | <b>证明</b> |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | <mo>⋅</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>c</mi> |
| | | <mo>⋅</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>⋅</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>⋅</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <mn>1</mn> |
| | | </math>. |
| | | </p> |
| | | <p>设</p> |
| | | <math display="block"> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mi mathvariant="bold">N</mi> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mtext>, 且 </mtext> |
| | | <mi>a</mi> |
| | | <mo>≠</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mtext>, </mtext> |
| | | </math> |
| | | <p class="right">①</p> |
| | | <p>由对数定义得</p> |
| | | <math display="block"> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mi mathvariant="bold">N</mi> |
| | | <mo>,</mo> |
| | | </math> |
| | | <p class="right">②</p> |
| | | <p>把②代入①中,得</p> |
| | | <math display="block"> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mi mathvariant="bold">N</mi> |
| | | <mo stretchy="false">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mtext>, 且 </mtext> |
| | | <mi>a</mi> |
| | | <mo>≠</mo> |
| | | <mn>1</mn> |
| | | <mo stretchy="false">)</mo> |
| | | <mtext>. </mtext> |
| | | </math> |
| | | <p>这个式子叫<b>对数恒等式</b>.</p> |
| | | <p> |
| | | <span class="zt-ls"><b>例3</b></span> 求下列各式的值. |
| | | </p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | </math>;(2) |
| | | <math display="0"> |
| | | <msup> |
| | | <mn>4</mn> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | </math>;(3) |
| | | <math display="0"> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(1)</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mn>7</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(2)</mo> |
| | | <msup> |
| | | <mn>4</mn> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>7</mn> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msup> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>49</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mn>49</mn> |
| | | <mo>;</mo> |
| | | </math> |
| | | </p> |
| | | <p class="left1"> |
| | | <math display=""> |
| | | <mo stretchy="false">(3)</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | <mo>+</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <mn>1</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>×</mo> |
| | | <msup> |
| | | <mn>2</mn> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>2</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mn>7</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mn>2</mn> |
| | | <mo>×</mo> |
| | | <mn>7</mn> |
| | | <mo>=</mo> |
| | | <mn>14</mn> |
| | | <mo>.</mo> |
| | | </math> |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[141]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 135 --> |
| | | <div class="page-box" page="142"> |
| | | <div v-if="showPageList.indexOf(142) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>135</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c043">习题4.3<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[142]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <h2 id="b025"> |
| | | 4.4 对数函数<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <h3 id="c044"> |
| | | 4.4.1 对数函数的定义<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/wttc.jpg" /> |
| | | </p> |
| | | <p> |
| | | 在第二节“观察思考”的情境2中,细胞由1个分裂为2个,2个分裂为4个……如果已知分裂<i>x</i>次后对应细胞数量是1 |
| | | 024个,那么如何求分裂的次数<i>x</i>呢? |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | |
| | | <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> |
| | | 设1个细胞经过<i>y</i>次分裂后得到<i>x</i>个细胞,则<i>x</i>与<i>y</i>的函数关系式为<i>x</i>=2<i><sup>y</sup></i>,将此指数式写为对数式,得到 |
| | | </p> |
| | | <p class="center"><i>y</i>=log<sub>2</sub><i>x</i>.</p> |
| | | <p>这个式子就是用分裂后的细胞数量<i>x</i>来表示分裂的次数<i>y</i>.</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">对数函数</p> |
| | | </div> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 通过指数与对数的关系我们观察到:<i>y</i>=log<sub>2</sub><i>x</i>是一个函数,其自变量<i>x</i>位于真数位置,底数是常数.类比指数函数定义的学习过程,我们可以用字母<i>a</i>代替底数2,即有<i>y</i>=log<sub>a</sub><i>x</i>(<i>a</i>>0,且<i>a</i>≠1)这类特征的函数. |
| | | </p> |
| | | <p> |
| | | 一般地,形如<i>y</i>=log<i><sub>a</sub>x</i>(<i>a</i>>0,且<i>a</i>≠1)的函数叫作<b>对数函数</b>,其中<i>x</i>是自变量,函数的定义域为(0,+∞). |
| | | </p> |
| | | <p> |
| | | 例如,<i>y</i>=log<sub>2</sub><i>x</i>,<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </math>,<i>y</i>=lg <i>x</i>,<i>y</i>=ln <i>x</i>都是对数函数. |
| | | </p> |
| | | <div class="bk"> |
| | | <div class="bj1"> |
| | | <p class="left"> |
| | | <img class="img-gn1" alt="" src="../../assets/images/tbts.jpg" /> |
| | | </p> |
| | | </div> |
| | | <p class="block"> |
| | | 1.对数函数与指数函数的底数<i>a</i>的取值范围保持一致. |
| | | </p> |
| | | <p class="block">2.由于对数的</p> |
| | | <p class="block"> |
| | | 真数的取值范围为(0,+∞),所以对数函数自变量<i>x</i>的取值范围为(0,+∞). |
| | | </p> |
| | | </div> |
| | | <p> |
| | | <span |
| | | class="zt-ls"><b>例1</b></span> 已知对数函数<i>f</i>(<i>x</i>)=log<i><sub>a</sub>x</i>(<i>a</i>>0,且<i>a</i>≠1),且<i>f</i>(9)= |
| | | 2,求<i>f</i>(3),<i>f</i>(1),<math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>27</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>的值. |
| | | </p> |
| | | <p class="block"> |
| | | <span class="zt-ls2"><b>分析</b></span> 首先根据条件确定底数<i>a</i>,然后再计算对应函数值. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 因为<i>f</i>(9)=2,得2=log<i><sub>a</sub></i>9. |
| | | </p> |
| | | <p>于是<i>a</i><sup>2</sup>=9,得<i>a</i>=3,</p> |
| | | <p>函数解析式为<i>f</i>(<i>x</i>)=log<sub>3</sub><i>x</i>.</p> |
| | | <p> |
| | | 所以<i>f</i>(3)=log<sub>3</sub>3=1, |
| | | <i>f</i>(1)=log<sub>3</sub>1=0, |
| | | </p> |
| | | <p> |
| | | <math display="0"> |
| | | <mi>f</mi> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>27</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>27</mn> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <msup> |
| | | <mn>3</mn> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mn>3</mn> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 求下列函数的定义域. |
| | | </p> |
| | | <p> |
| | | (1) <i>y</i>=log <sub>0.5</sub>(<i>x</i>-3);(2) |
| | | <i>y</i>=log<sub>3</sub>(4-<i>x</i><sup>2</sup>). |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 要使函数有意义,必须满足<i>x</i>-3>0,解得<i>x</i>>3. |
| | | </p> |
| | | <p> |
| | | 所以,<i>y</i>=log <sub>0.5</sub>(<i>x</i>-3)的定义域是(3,+∞). |
| | | </p> |
| | | <p> |
| | | (2) 要使函数有意义,必须满足4-<i>x</i><sup>2</sup>>0,解得 |
| | | -2<<i>x</i><2. |
| | | </p> |
| | | <p> |
| | | 所以,<i>y</i>=log<sub>3</sub>(4-<i>x</i><sup>2</sup>)的定义域是(-2,2). |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 137 --> |
| | | <div class="page-box" page="144"> |
| | | <div v-if="showPageList.indexOf(144) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</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[144]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | <h3 id="c045"> |
| | | 4.4.2 对数函数的图像与性质<span class="fontsz2">>>></span> |
| | | </h3> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/gcsk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 与研究指数函数的图像和性质一样,我们首先通过描点法画出对数函数的图像,然后归纳总结函数的相关性质.下面我们以<i>y</i>=log<sub>2</sub><i>x</i>和<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </math>为例画出对数函数的图像,通过观察其图像特征,归纳出对数函数的性质. |
| | | </p> |
| | | <p>第一步:计算部分数值并列表(如表4-5所示).</p> |
| | | <p class="img">表4-5</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0148-3.jpg" /> |
| | | </p> |
| | | <p> |
| | | 第二步:描点,并用光滑的曲线连接所描的点,画出它们的图像,如图4-8所示. |
| | | </p> |
| | | <p> |
| | | 利用相同方法,我们还可以在同一平面直角坐标系中画出<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </math>,<i>y</i>=log <sub>2</sub><i>x</i>,<i>y</i>=log <sub>0.08</sub><i>x</i>,<i>y</i>=log |
| | | <sub>4.5</sub><i>x</i>,<i>y</i>=log |
| | | <sub>0.6</sub><i>x</i>,<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </math>的图像,如图4-9所示. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 138 --> |
| | | <div class="page-box" page="145"> |
| | | <div v-if="showPageList.indexOf(145) > -1"> |
| | | |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>138</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="center"> |
| | | <img class="img-c" alt="" src="../../assets/images/0149-1.jpg" /> |
| | | </p> |
| | | <p class="img">图4-8</p> |
| | | <p class="center"> |
| | | <img class="img-c" alt="" src="../../assets/images/0149-2.jpg" /> |
| | | </p> |
| | | <p class="img">图4-9</p> |
| | | <p><b>类比归纳</b></p> |
| | | <p> |
| | | 类比指数函数图像特征的观察方法,观察对数函数的图像,描述它们的图像在位置、公共点和变化趋势等方面的共性特征. |
| | | </p> |
| | | <p> |
| | | (1) |
| | | 图中所有对数函数的图像均在<i>y</i>轴的右侧(<b>位置特征</b>); |
| | | </p> |
| | | <p> |
| | | (2) |
| | | 图中所有对数函数的图像都经过定点(1,0)(<b>公共点特征</b>); |
| | | </p> |
| | | <p> |
| | | (3) 在定义域内,对数函数<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>3</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </math>,<i>y</i>=log <sub>2</sub><i>x</i>,<i>y</i>=log |
| | | <sub>4.5</sub><i>x</i>图像从左到右分别逐渐上升,在第四象限内向下与<i>y</i>轴无限接近;对数函数<i>y</i>=log |
| | | <sub>0.08</sub><i>x</i>,<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </math>,<i>y</i>=log <sub>0.6</sub><i>x</i>图像从左到右分别逐渐下降,在第一象限内向上与<i>y</i>轴无限接近(<b>变化趋势特征</b>). |
| | | </p> |
| | | <p> |
| | | 类比指数函数的图像,对数函数<i>y</i>=log<i><sub>a</sub>x</i>(<i>a</i>>0,且<i>a</i>≠1)的图像按底数<i>a</i>的取值,可分为0<<i>a</i><1和<i>a</i>>1两种类型,我们从指数式与对数式的关系也可发现. |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/cxgk.jpg" /> |
| | | </p> |
| | | <p> |
| | | 一般地,对数函数<i>y</i>=log<i><sub>a</sub>x</i>(<i>a</i>>0,且<i>a</i>≠1)具有下列性质. |
| | | </p> |
| | | <p>(1) 函数的定义域为(0,+∞),值域为<b>R</b>;</p> |
| | | <p>(2) 当<i>x</i>=1时,函数值<i>y</i>=0;</p> |
| | | <p> |
| | | (3) |
| | | 当<i>a</i>>1时,函数在(0,+∞)内是增函数;当0<<i>a</i><1时,函数在(0,+∞)内是减函数. |
| | | </p> |
| | | <p>对数函数的图像和性质可以总结如表4-6所示.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 139 --> |
| | | <div class="page-box" page="146"> |
| | | <div v-if="showPageList.indexOf(146) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>139</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p class="img">表4-6</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0150-1.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> |
| | | <p class="block"> |
| | | 1.你还能从图4-10中观察发现其他共性特征吗?比如,对数函数<i>y</i>=log |
| | | 2<i>x</i>和<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>2</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </math>的图像有什么关系? |
| | | </p> |
| | | <p class="block"> |
| | | 2.两人一组,一人用表格呈现指数函数的图像与性质,另一人用表格呈现对数函数的图像与性质,然后对比两个函数的图像与性质,归纳总结为一个表格,并与同学交流分享. |
| | | </p> |
| | | </div> |
| | | <p> |
| | | <span class="zt-ls"><b>例1</b></span> 比较下列各组数中两个值的大小. |
| | | </p> |
| | | <p> |
| | | (1) log<sub>2</sub>5.3 与log<sub>2</sub>4.7;(2) log |
| | | <sub>0.2</sub>7与log <sub>0.2</sub>9; |
| | | </p> |
| | | <p> |
| | | (3) log<sub>5</sub>4与1;(4)log<sub>3</sub>4与log |
| | | <sub>0.3</sub>4. |
| | | </p> |
| | | <p class="block"> |
| | | <span class="zt-ls2"><b>分析</b></span> 若两个对数的底数相同,可利用对数函数的单调性直接比较;若底数不同,可采用先与中间量(通常是0或1)进行比较,再利用不等式传递性得出结论. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) |
| | | 因为底数2>1,所以<i>y</i>=log<sub>2</sub><i>x</i>在区间(0,+∞)上是增函数,函数图像如图4-10所示. |
| | | </p> |
| | | <p>又因为5.3>4.7,所以log<sub>2</sub>5.3>log<sub>2</sub>4.7.</p> |
| | | <p> |
| | | (2) 因为底数0<0.2<1,所以<i>y</i>=log <sub>0.2</sub><i>x</i>在区间(0,+∞)上是减函数,函数图像如图4-11所示. |
| | | </p> |
| | | <p>又因为7<9,所以log <sub>0.2</sub>7>log <sub>0.2</sub>9.</p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | (3) log<sub>5</sub>4<log<sub>5</sub>5=1,即log<sub>5</sub>4<1. |
| | | </p> |
| | | <ul class="fl"> |
| | | <li> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0151-1.jpg" /> |
| | | </p> |
| | | <p class="img">图4-10</p> |
| | | </li> |
| | | <li> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0151-2.jpg" /> |
| | | </p> |
| | | <p class="img">图4-11</p> |
| | | </li> |
| | | </ul> |
| | | <p> |
| | | (4) 因为 log<sub>3</sub>4>log<sub>3</sub>1=0,log |
| | | <sub>0.3</sub>4<log <sub>0.3</sub>1=0,所以 log<sub>3</sub>4>log |
| | | <sub>0.3</sub>4. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 解下列不等式. |
| | | </p> |
| | | <p> |
| | | (1)log <sub>4</sub><i>x</i><log<sub>4</sub>5;(2) |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>1</mn> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 因为<i>y</i>=log |
| | | 4<i>x</i>在(0,+∞)上是增函数,所以<i>x</i><5. |
| | | </p> |
| | | <p>又因为<i>x</i>>0,所以0<<i>x</i><5.</p> |
| | | <p>所以不等式的解集为(0,5).</p> |
| | | <p> |
| | | (2) |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <mn>1</mn> |
| | | </math>,即<math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | <mo>></mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 因为<math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </math>在(0,+∞)上是减函数,所以<math display="0"> |
| | | <mi>x</mi> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 又因为<i>x</i>>0,所以<math display="0"> |
| | | <mn>0</mn> |
| | | <mo><</mo> |
| | | <mi>x</mi> |
| | | <mo><</mo> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 所以不等式的解集为(0,<math display="0"> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mfrac> |
| | | <mn>4</mn> |
| | | <mn>5</mn> |
| | | </mfrac> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>). |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/stlx.jpg" /> |
| | | </p> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[147]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 141 --> |
| | | <div class="page-box" page="148"> |
| | | <div v-if="showPageList.indexOf(148) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>141</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c046">习题4.4<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[148]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <div class="bj"> |
| | | <p>A.(0,1)</p> |
| | | <p>B.(1,2)</p> |
| | | <p>C.(1,+∞)</p> |
| | | <p>D.(0,2)</p> |
| | | <p> |
| | | (3) 函数<i>y</i>=3+log<i><sub>a</sub>x</i>(<i>a</i>>0,且<i>a</i>≠1)的图像过定点( ). |
| | | </p> |
| | | <p>A.(0,1)</p> |
| | | <p>B.(1,0)</p> |
| | | <p>C.(1,3)</p> |
| | | <p>D.(1,4)</p> |
| | | <p> |
| | | (4) 已知log<sub>0.5</sub><i>x</i>>log<sub>0.5</sub>3,则<i>x</i>的取值范围是( ). |
| | | </p> |
| | | <p>A.(3,+∞)</p> |
| | | <p>B.(0,+∞)</p> |
| | | <p>C.(-∞,3)</p> |
| | | <p>D.(0,3)</p> |
| | | <p> |
| | | (5) |
| | | 已知<i>a</i>=log<sub>0.7</sub>0.8,<i>b</i>=log<sub>0.7</sub>1.9,<i>c</i>=log<sub>5</sub>1,则<i>a</i>,<i>b</i>,<i>c</i>的大小关系是( ). |
| | | </p> |
| | | <p>A.<i>a</i><<i>b</i><<i>c</i></p> |
| | | <p>B.<i>a</i><<i>c</i><<i>b</i></p> |
| | | <p>C.<i>b</i><<i>a</i><<i>c</i></p> |
| | | <p>D.<i>b</i><<i>c</i><<i>a</i></p> |
| | | <p>2.求下列函数的定义域.</p> |
| | | <p> |
| | | (1) |
| | | <math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mi>x</mi> |
| | | <msqrt> |
| | | <mn>1</mn> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mn>3</mn> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </msqrt> |
| | | </mfrac> |
| | | </math>;(2) |
| | | <math display="0"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <msqrt> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>4</mn> |
| | | </mfrac> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | </msqrt> |
| | | </math>. |
| | | </p> |
| | | <p> |
| | | 3.已知函数<i>f</i>(<i>x</i>)=log<i><sub>a</sub>x</i>(<i>a</i>>0,且<i>a</i>≠1)的图像过点(9,-2),求<i>f</i>(3)的值. |
| | | </p> |
| | | <p> |
| | | 4.我国经济总量占世界经济的比重达18.5%,居世界第二位.2020年我国全年<i>GDP</i>为1 |
| | | 015 |
| | | 986亿元,取得了超过100万亿的历史性成就.2021年我国<i>GDP</i>预期目标是增长率超过6.0%.假设我国每年<i>GDP</i>的增长率均为6.0%,从2021年开始,大约经过多少年,我国能实现全年<i>GDP</i>比2021年翻一番? |
| | | </p> |
| | | </div> |
| | | <h2 id="b026"> |
| | | 4.5 指数函数与对数函数的实际应用<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <p> |
| | | 我们学习的基本初等函数,可以描述、刻画客观世界中某一类事物运动变化的规律.例如,用一次函数模型可以描述生活中的“线性增长”(直线增长)现象.利用指数函数与对数函数的相关知识建立函数模型,可以描述、刻画科学与技术、经济与社会、生产与生活中的“指数增长”和“对数增长”现象. |
| | | </p> |
| | | <p> |
| | | <span |
| | | class="zt-ls"><b>例1</b></span> 开展人口普查,对于调整、完善人口政策,推动人口结构优化,促进人口素质提升具有重要意义.第七次全国人口普查结果显示,2020年年末全国大陆总人口为141 |
| | | 178万人,其中城镇常住人口90 |
| | | 199万人,占总人口的比例(常住人口城镇化率)为63.89%,与2010年相比,提高了14.21个百分点. |
| | | </p> |
| | | <p> |
| | | (1) 假设此后每年都增加700万人口,20年后我国大陆人口总数是多少? |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 143 --> |
| | | <div class="page-box" page="150"> |
| | | <div v-if="showPageList.indexOf(150) > -1"> |
| | | |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>143</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | (2) |
| | | 假设此后每年人口的平均增长率是1%(每年都在前一年基础上增加1%),20年后我国大陆人口总数约为多少?(单位:万,结果精确到0.01) |
| | | </p> |
| | | <p class="block"> |
| | | <b>分析</b>(1) |
| | | 这是经济社会中的“线性增长”现象,即每年增加量保持不变,每年增加700万人口,20年共增加14 |
| | | 000万人口,因此总共人口为155 178万. |
| | | </p> |
| | | <p class="block"> |
| | | (2) |
| | | 这是经济社会中的“指数增长”现象,即每年按照一定的增长率(成倍数)增长.我们首先考查逐年增长的情况,从中发现每一年都是前一年的(1+1%)倍(也可采用后一年与前一年的比值发现规律),即呈指数增长,最后利用指数函数知识解决问题. |
| | | </p> |
| | | <p class="block">2020年年末 人口约为141 178万;</p> |
| | | <p class="block">经过1年 人口约为141 178(1+1%)万;</p> |
| | | <p class="block"> |
| | | 经过2年 人口约为141 178(1+1%)(1+1%)=141 |
| | | 178(1+1%)<sup>2</sup>万; |
| | | </p> |
| | | <p class="block"> |
| | | 经过3年 人口约为141 178(1+1%)<sup>2</sup>(1+1%)=141 |
| | | 178(1+1%)<sup>3</sup>万; |
| | | </p> |
| | | <p class="block">……</p> |
| | | <p class="block"> |
| | | 经过<i>x</i>年 人口约为141 178(1+1%)<i><sup>x</sup></i>万. |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span>(1) 因为每年增加700万人口,20年共增加20×700万=14 |
| | | 000万人口,因此20年后我国大陆人口为155 178万(15.517 8亿). |
| | | </p> |
| | | <p>(2) 设经过<i>x</i>年,我国人口为<i>y</i>万,由题意得</p> |
| | | <p class="center"> |
| | | <i>y</i>=141 178(1+1%)<i><sup>x</sup></i>. |
| | | </p> |
| | | <p>当<i>x</i>=20时,<i>y</i>=141 178(1+1%)<sup>20</sup>.</p> |
| | | <p>利用科学计算器可求得<i>y</i>≈172 263.99万.</p> |
| | | <p> |
| | | 所以,假设每年都增加700万人口,20年后我国大陆人口为155 |
| | | 178万;假设每年人口的平均增长率是1%,经过20年后我国大陆人口约为172 |
| | | 263.99万. |
| | | </p> |
| | | <p class="left"> |
| | | <img class="img-gn" alt="" src="../../assets/images/fxlj.jpg" /> |
| | | </p> |
| | | <p> |
| | | 比较两种增长方式,随着时间推移,“指数增长”方式更具有爆发性.探究两种增长方式的特点,并分别列举社会生活中的“线性增长”和“指数增长”现象. |
| | | </p> |
| | | <p> |
| | | 一般地,形如<i>y</i>=<i>ka<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1,<i>k</i>≠0)的函数称为<b>指数型函数</b>,这是生活实际中常见的和实用的函数模型.其中,当<i>a</i>>1时,该函数叫作指数增长模型,如我们常说的“指数爆炸”现象所蕴含的就是这种模型;当0<<i>a</i><1时,该函数叫作指数衰减模型,如考古工作中的碳14衰减现象所蕴含的就是这种模型. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 144 --> |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p> |
| | | <span class="zt-ls"><b>例2</b></span> 2020年12月8日,中国、尼泊尔两国共同向全世界正式宣布,世界第一高峰珠穆朗玛峰的最新海拔高程为8 |
| | | 848.86 |
| | | m.由于珠穆朗玛峰气候多变、高寒缺氧、环境复杂,对测量装备、测绘技术和测绘人员有很高的要求,因此精确测量珠穆朗玛峰高程是一个国家测绘技术水平和能力的综合体现.已知海拔高程<i>y</i>(m) |
| | | 与大气压强<i>x</i>(Pa)之间的关系可用函数 <i>y</i>=<i>k</i> ln |
| | | <i>x</i>+<i>c</i> |
| | | 来近似描述,其中<i>c</i>,<i>k</i>可看成常量.又知登顶过程中,海平面的大气压强为1.013×10<sup>5</sup> |
| | | Pa,北坳营地海拔7 028 m,大气压强约为4.21×10<sup>4</sup>Pa. |
| | | </p> |
| | | <p> |
| | | (1) 当大气压强为3.81×10<sup>4</sup> <i>Pa</i> 时,海拔高程是多少? |
| | | </p> |
| | | <p> |
| | | (2) 当测绘人员在登顶过程中测得其所在位置的海拔高程为8 844.43 |
| | | m时,大气压强为多少? |
| | | </p> |
| | | <p> |
| | | <span class="zt-ls"><b>解</b></span> 海平面的海拔高程为0 m.将 |
| | | </p> |
| | | <p class="center"> |
| | | <i>x</i><sub>1</sub>=1.013×10<sup>5</sup>,<i>y</i><sub>1</sub>=0, |
| | | </p> |
| | | <p class="center"> |
| | | <i>x</i><sub>2</sub>=4.21×10<sup>4</sup>,<i>y</i><sub>2</sub>=7 |
| | | 028, |
| | | </p> |
| | | <p>分别代入函数关系式 <i>y</i>=<i>k</i> ln <i>x</i>+<i>c</i>,</p> |
| | | <p>解得 <i>k</i>≈-8 004.203,<i>c</i>≈92 255.180.</p> |
| | | <p>于是,大气压强与海拔高程的关系式近似为</p> |
| | | <math display="block"> |
| | | <mi>y</mi> |
| | | <mo>=</mo> |
| | | <mo>−</mo> |
| | | <mn>8004.203</mn> |
| | | <mi>ln</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>x</mi> |
| | | <mo>+</mo> |
| | | <mn>92255.180</mn> |
| | | <mo>.</mo> |
| | | </math> |
| | | <p class="right">①</p> |
| | | <p>(1) 当<i>x</i>=3.81×10<sup>4</sup>时,</p> |
| | | <p><i>y</i>=-8 004.203×ln(3.81×10<sup>4</sup>)+92 255.180</p> |
| | | <p>≈7 827.090.</p> |
| | | <p> |
| | | 所以,当大气压强为3.81×10<sup>4</sup> <i>Pa</i>时,海拔高程约为7 |
| | | 827.090 m. |
| | | </p> |
| | | <p>(2) 把<i>y</i>=8 844.43代入①式,</p> |
| | | <p class="center">8 844.43=-8 004.203 ln <i>x</i>+92 255.180,</p> |
| | | <p class="center"> |
| | | ln <i>x</i>=10.421⇒<i>x</i>=<i>e</i><sup>10.421</sup>≈33 |
| | | 556.974≈3.36×10<sup>4</sup>. |
| | | </p> |
| | | <p> |
| | | 所以,当测绘人员在登顶过程中测得其所在位置的海拔高程为8 844.43 |
| | | m时,大气压强约为3.36×10<sup>4</sup> |
| | | <i>Pa</i>,约为海平面大气压强的<math display="0"> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <mn>3</mn> |
| | | </mfrac> |
| | | </math>. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 145 --> |
| | | <div class="page-box" page="152"> |
| | | <div v-if="showPageList.indexOf(152) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | | </li> |
| | | <li> |
| | | <p><span>145</span></p> |
| | | <p><span>145-146</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h3 id="c047">习题4.5<span class="fontsz2">>>></span></h3> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[152]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 146 --> |
| | | <div class="page-box" page="153"> |
| | | <div v-if="showPageList.indexOf(153) > -1"> |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>146</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | </div> |
| | | </div> |
| | | <div class="page-box hidePage" page="153"></div> |
| | | |
| | | <!-- 147 --> |
| | | <div class="page-box" page="154"> |
| | | <div v-if="showPageList.indexOf(154) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>147</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h2 id="b027"> |
| | | 数学园地<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <p class="center">我们身边的“指数爆炸”</p> |
| | | <p> |
| | | “指数爆炸”不是真正的爆炸,是事物数量的变化呈现爆炸式急剧增长时的现象.用数学语言描述该现象时,可用指数函数模型<i>f</i>(<i>x</i>)=<i>ka<sup>x</sup></i>(<i>a</i>>1)来刻画这种变化规律,这种增长方式也叫作“指数增长”. |
| | | </p> |
| | | <p> |
| | | 在幼儿园、小学阶段,同学们经常玩的折纸游戏也蕴含着“指数爆炸”的道理.一张足够大、足够柔软的纸片每对折一次,纸片的厚度就会翻一番,如果持续对折下去,其厚度增长是“爆炸式”的.一张足够大的1 |
| | | mm厚的纸片如果连续对折42次,其厚度大约为4.4×10<sup>5</sup> |
| | | km,可以直接从地球连到月球了(地球与月球之间的距离约为3.8×10<sup>5</sup> |
| | | km). |
| | | </p> |
| | | <p> |
| | | 在卫生健康方面,我们几乎每天都在和细菌打交道,因为很多细菌的繁殖速度都是呈“指数爆炸”式的.有研究显示,一双未洗过的手上大约有80万个细菌,假设某种细菌以二分裂法繁殖(每分裂一次,数量是原来的两倍),每5秒分裂一次,很快,这双未洗过的手上的细菌就会增长到5 |
| | | 000多万个,庞大的细菌群体经常会导致我们“病从手入”.所以,保持饭前便后洗手的良好卫生习惯,对我们身体健康有着至关重要的作用. |
| | | </p> |
| | | <p> |
| | | 在旅游服务领域,一些消费性政策可能会导致游客人数的“爆炸式”增长.例如,某一景区为吸引更多游客,从2001年开始,施行门票免费活动,游客人数从30万人次增加到2020年的220万人次,平均每年增加1.11倍,这也蕴含着“指数增长”.如果游客人数增长过度,会出现景区人满为患、服务跟不上等问题,因此需要利用函数模型预测未来变化趋势,合理施行旅游活动. |
| | | </p> |
| | | <p> |
| | | 从细如发丝的拉面、折纸游戏、细菌繁殖,到景区旅游、银行储蓄等,都与“指数爆炸”有着千丝万缕的联系.在客观世界中,数学早已悄悄潜入我们生活、工作的方方面面. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h2 id="b028"> |
| | | 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/0159-1.jpg" /> |
| | | </p> |
| | | <p class="bj2"><b>学习指导</b></p> |
| | | <p>1.实数指数幂.</p> |
| | | <p>(1) 正整数、负整数、分数、指数幂的意义.</p> |
| | | <p> |
| | | ①<math display="0"> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <munder> |
| | | <mrow data-mjx-texclass="OP"> |
| | | <munder> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | <mo>⋅</mo> |
| | | <mi>a</mi> |
| | | <mo>⋅</mo> |
| | | <mi>a</mi> |
| | | <mo>⋅</mo> |
| | | <mo>⋯</mo> |
| | | <mo>⋅</mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | <mo>⏟</mo> |
| | | </munder> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | <mo stretchy="false">↑</mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </munder> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>n</mi> |
| | | <mo>∈</mo> |
| | | <msub> |
| | | <mrow> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>+</mo> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>; ②<math display="0"> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mo>−</mo> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mn>1</mn> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>n</mi> |
| | | </mrow> |
| | | </msup> |
| | | </mfrac> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>a</mi> |
| | | <mo>≠</mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mi>n</mi> |
| | | <mo>∈</mo> |
| | | <msub> |
| | | <mrow> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>+</mo> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | ③<math display="0"> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mfrac> |
| | | <mi>m</mi> |
| | | <mi>n</mi> |
| | | </mfrac> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mroot> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <mi>m</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mi>n</mi> |
| | | </mroot> |
| | | <mrow data-mjx-texclass="INNER"> |
| | | <mo data-mjx-texclass="OPEN">(</mo> |
| | | <mi>a</mi> |
| | | <mo>></mo> |
| | | <mn>0</mn> |
| | | <mo>,</mo> |
| | | <mi>m</mi> |
| | | <mo>,</mo> |
| | | <mi>n</mi> |
| | | <mo>∈</mo> |
| | | <msub> |
| | | <mrow> |
| | | <mi mathvariant="bold">N</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mo>+</mo> |
| | | </mrow> |
| | | </msub> |
| | | <mo>,</mo> |
| | | <mi>n</mi> |
| | | <mo>></mo> |
| | | <mn>1</mn> |
| | | <mo data-mjx-texclass="CLOSE">)</mo> |
| | | </mrow> |
| | | </math>. |
| | | </p> |
| | | <p>(2) 运算性质.</p> |
| | | <p>设<i>a</i>>0,<i>b</i>>0,<i>m</i>,<i>n</i>∈<b>R</b>,则</p> |
| | | <p> |
| | | ①<i>a<sup>m</sup> |
| | | a<sup>n</sup></i>=<i>a<sup>m+n</sup></i>; ②(<i>a<sup>m</sup></i>)<i><sup>n</sup></i>=<i>a<sup>mn</sup></i>; ③(<i>ab</i>)<i><sup>n</sup></i>=<i>a<sup>n</sup> |
| | | b<sup>n</sup></i>. |
| | | </p> |
| | | <p>2.对数.</p> |
| | | <p> |
| | | (1) |
| | | 定义:如果<i>a<sup>x</sup></i>=<i>N</i>(<i>a</i>>0,且<i>a</i>≠1),那么数<i>x</i>叫作以<i>a</i>为底<i>N</i>的<b>对数</b>,记作<i>x</i>=log<i><sub>a</sub>N</i>,其中<i>a</i>叫作对数的<b>底数</b>(简称底),<i>N</i>叫作<b>真数</b>. |
| | | </p> |
| | | <p> |
| | | 通常我们把log <sub>10</sub><i>N</i>叫作常用对数,简记作lg <i>N</i>; |
| | | 把log<sub>e</sub><i>N</i>叫作自然对数,简记作ln <i>N</i>. |
| | | </p> |
| | | <p> |
| | | (2) 性质:①零和负数没有对数;②log<i><sub>a</sub></i>1=0,即1的对数为0;③log<i><sub>a</sub>a</i>=1,即底数的对数为1. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | | <!-- 149 --> |
| | | <div class="page-box" page="156"> |
| | | <div v-if="showPageList.indexOf(156) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | |
| | | <p><span>149</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <p>(3) 运算法则.</p> |
| | | <p> |
| | | ①log<i><sub>a</sub></i>(<i>MN</i>)=log<i><sub>a</sub>M</i>+log<i><sub>a</sub>N</i>; ②<math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mfrac> |
| | | <mi>M</mi> |
| | | <mi>N</mi> |
| | | </mfrac> |
| | | <mo>=</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>M</mi> |
| | | <mo>−</mo> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>N</mi> |
| | | </math>; |
| | | </p> |
| | | <p> |
| | | ③log<i><sub>a</sub>N<sup>n</sup></i>=<i>n</i>log |
| | | <i><sub>a</sub>N</i>(<i>a</i>>0,且<i>a</i>≠1,<i>n</i>∈<b>R</b>). |
| | | </p> |
| | | <p>(4)(选学)换底公式.</p> |
| | | <p> |
| | | <math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>c</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>(<i>a</i>>0,且<i>a</i>≠1;<i>c</i>>0,且<i>c</i>≠1). |
| | | </p> |
| | | <p> |
| | | 特别地,<math display="0"> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | <mo>=</mo> |
| | | <mfrac> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>b</mi> |
| | | </mrow> |
| | | <mrow> |
| | | <mi>lg</mi> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </mfrac> |
| | | </math>(<i>a</i>>0,且<i>a</i>≠1). |
| | | </p> |
| | | <p> |
| | | 对数恒等式:<math display="0"> |
| | | <msup> |
| | | <mi>a</mi> |
| | | <mrow> |
| | | <msub> |
| | | <mi>log</mi> |
| | | <mrow> |
| | | <mi>a</mi> |
| | | </mrow> |
| | | </msub> |
| | | <mo data-mjx-texclass="NONE"></mo> |
| | | <mi>N</mi> |
| | | </mrow> |
| | | </msup> |
| | | <mo>=</mo> |
| | | <mi>N</mi> |
| | | </math>(<i>a</i>>0,且<i>a</i>≠1). |
| | | </p> |
| | | <p>3.指数函数与对数函数.</p> |
| | | <p>(1) 定义.</p> |
| | | <p> |
| | | 形如<i>y</i>=<i>a<sup>x</sup></i>(<i>a</i>>0,且<i>a</i>≠1)的函数叫指数函数;形如<i>y</i>=log<i> |
| | | ax</i>(<i>a</i>>0,且<i>a</i>≠1)的函数叫对数函数. |
| | | </p> |
| | | <p>(2) 图像和性质.</p> |
| | | <p class="center"> |
| | | <img class="img-a" alt="" src="../../assets/images/0160-5.jpg" /> |
| | | </p> |
| | | <p>4.指数函数与对数函数的实际应用.</p> |
| | | <p> |
| | | 分析实例背景,建立指数函数或对数函数模型,并利用指数函数、对数函数的图像及基本性质解决简单的实际问题.体会“指数爆炸”与“指数衰减”的特点. |
| | | </p> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | |
| | |
| | | <div class="page-box" page="157"> |
| | | <div v-if="showPageList.indexOf(157) > -1"> |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>150</li> |
| | | <li>150-152</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116"></div> |
| | | <div class="padding-116"> |
| | | <h2 id="b029"> |
| | | 单元检测<span class="fontsz1">>>>>>>>></span> |
| | | </h2> |
| | | <div class="bj"> |
| | | <examinations :cardList="questionData[157]" :hideCollect="true" sourceType="json" v-if="questionData"> |
| | | </examinations> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | </div> |
| | | <!-- 151 --> |
| | | <div class="page-box" page="158"> |
| | | <div v-if="showPageList.indexOf(158) > -1"> |
| | | |
| | | <ul class="page-header-box"> |
| | | <li> |
| | | <p>第四单元 指数函数与对数函数</p> |
| | | </li> |
| | | <li> |
| | | <p><span>151</span></p> |
| | | </li> |
| | | </ul> |
| | | <div class="padding-116">158</div> |
| | | </div> |
| | | </div> |
| | | <div class="page-box hidePage" page="158"></div> |
| | | <!-- 152 --> |
| | | <div class="page-box" page="159"> |
| | | <div v-if="showPageList.indexOf(159) > -1"> |
| | | <ul class="page-header-odd fl al-end"> |
| | | <li>152</li> |
| | | <li>数学.基础模块</li> |
| | | <li>上册</li> |
| | | </ul> |
| | | <div class="padding-116">159</div> |
| | | </div> |
| | | </div> |
| | | <div class="page-box hidePage" page="159"></div> |
| | | </div> |
| | | </template> |
| | | |
| | | <script> |
| | | import examinations from "@/components/examinations/index.vue"; |
| | | export default { |
| | | name: '', |
| | | name: "", |
| | | props: { |
| | | showPageList: { |
| | | type: Array, |
| | | default: [], |
| | | }, |
| | | questionData: { |
| | | type: Object, |
| | | }, |
| | | }, |
| | | components: {}, |
| | | components: { examinations }, |
| | | data() { |
| | | return {} |
| | | return {}; |
| | | }, |
| | | computed: {}, |
| | | watch: {}, |
| | | created() { }, |
| | | mounted() { }, |
| | | methods: {}, |
| | | } |
| | | }; |
| | | </script> |
| | | |
| | | <style lang="less" scoped></style> |