1 . 已知等比数列
的前
项和为
,
,
,求:
(1)数列
的通项公式;
(2)
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8998e39d9ba7d2d16780e904a97d00af.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1634761b31e7faf962ee6d1c9669ec8d.png)
(1)数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/27f90c472b3cbcd1da548cad9db5455c.png)
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2 . 若无穷等比数列
的各项和为
,首项
,公比为
,且
,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54673d6096a7042dc9279de042d28e94.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4687150af7db1509d20902672aa949d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
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3 . 求数列
,
,
,…的各项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e41604a4ea7302ea8749ef49dcfdca53.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef07e29d1ad272483701892d75686f3e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63f5ef0eb2edcaba1ab87491b5d70ad3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
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4 . 一个无穷等比数列的各项和为6,它各项的平方和为18,求它各项的立方和.
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5 . 在平面直角坐标系中,动点由坐标原点出发,先向右移动1个单位达到点
,然后沿原方向逆时针旋转90°的方向,移动
个单位达到点
,若照此无限继续下去,每次都沿逆时针方向旋转90°,移动上次移动距离的一半,求此动点的极限位置.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e92b8041e98e4f435acdbeb983efbe46.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9a9e83a7565752489c9aa4f20b3ad73f.png)
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解题方法
6 . 一个无穷等比数列前n项和的极限存在,记作S,首项为
,公比
,求S的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/039e4fe671d61e59b96ee525c9df43e8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411641715d7f5132c34f1d6eace8cd8b.png)
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7 . 一个无穷等比数列的公比q满足
,它的各项和等于6,这个数列的各项平方和等于18,求这个数列的首项
与公比q.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c679a17000041b4e796a61bfb0a919e5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
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8 . 如图,在边长为1的正方形ABCD中,取AD、BC中点的
、
,得矩形
;取
、DC的中点
、
,得一小矩形
;再取
、
的中点
、
,得一小矩形
;如此无限继续下去,求所有这些矩形的面积之和.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a18722354086c42e62334983fc50eb6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97c01fdc7bc471af0b264a04aef0823e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab3e0dba5705e1d749cfb21ebbb2ed93.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11ddc92d84d188c66b435664a7e7b5a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd3b9e816b14051f785aa5aae72b8eed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/43a71fc9c0068109dad1382354570665.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f422a862643435e0e81008d217af20c1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10d8eb4a9f462ca0c1d49c3fe91e720d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc34876d748f30fa4fc2eb6a686b5ff5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04b56e44e4f0424a2b7a45567120a2e4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2857fac4963b129d99e79dcb3e13d295.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f8066ebae7a11f1f6d1dc99436408dc.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/8/f5f616d9-dc75-4dad-a807-7e3498a28eb9.png?resizew=181)
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解题方法
9 . 无穷数列前n项和记为
,
,且
,求实数r的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0f357390ba0a45a573620987197c472.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/808c7ac7a05b4002cd9930e0f772f6de.png)
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10 . 将下列循环小数化为分数.
(1)
;
(2)
.
(1)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/281dc0e9885033eb8849390098ec144e.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad7a359e4e053fc2c6cfa6fbb137364.png)
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