1 . 等比数列
中,
,
,![](https://img.xkw.com/dksih/QBM/2016/2/29/1572503850123264/1572503855710208/STEM/2eb50df36acf4eb7a08b7dc40dce7d0e.png)
![](https://img.xkw.com/dksih/QBM/2016/2/29/1572503850123264/1572503855710208/STEM/ccbe81115bea4acaa4aa5ceadb9f0c4e.png)
![](https://img.xkw.com/dksih/QBM/2016/2/29/1572503850123264/1572503855710208/STEM/350c2f7cc08146aca3a8027db2dfa6bf.png)
![](https://img.xkw.com/dksih/QBM/2016/2/29/1572503850123264/1572503855710208/STEM/762eaac4946341d28537d8c29f072d76.png)
![](https://img.xkw.com/dksih/QBM/2016/2/29/1572503850123264/1572503855710208/STEM/2eb50df36acf4eb7a08b7dc40dce7d0e.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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2 . 已知数列
的前
项和为
,
且
,
(Ⅰ) 求证:对任意
,
,为常数
,并求出这个常数
;
(Ⅱ)如果
,求数列
的前
项的和.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29518f13a1ebc3fff8181c2d7cfba22f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b708c8dcb2d66eb2ce0b3718a9cd924a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9000ea6d9bfcf9a36236f4e54df18317.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/663bbc5767b9cb453cb08e1f0a8e0602.png)
(Ⅰ) 求证:对任意
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb8c29b297e3ec337c3139c2a1ebed1b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba2804670279f82c2b2acf56ce6b4f17.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
(Ⅱ)如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8520173e7e568a7529ccefaf0b1da97b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2448cf72af76b810310e4cfb9818e2e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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3 . 数列
的前
项和记为
,
,
.
(Ⅰ)当
为何值时,数列
是等比数列;
(Ⅱ)在(I)的条件下,若等差数列
的前
项和
有最大值,且
,
又
,
,
成等比数列,求
.
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/a14874924f974663b6228edefe007c62.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/111c61029e5a4e6d8fa89d9b33d4e052.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/38a4909d26f54cd89ea702151c9e3804.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/c896b2c7c68847cab3078f44fb9cdc36.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/92f411101a005149144330ec9b834aa8.png)
(Ⅰ)当
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/f179c2d8888046a5afd7fe2911bbc71a.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/a14874924f974663b6228edefe007c62.png)
(Ⅱ)在(I)的条件下,若等差数列
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/651da324eae6433caa2fdcc488a1283e.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/111c61029e5a4e6d8fa89d9b33d4e052.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/2ddbdccb3bac4f048069fb42ba6627a2.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/45fbbe3dec5f48ce8c8b4d4c1b753558.png)
又
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/c9ed6071929243f3bb2ad7a9d84d1682.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/20846b8a021e4e36935861dc67b3ed62.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/b3a2782e5e8a44e88e7d401f604acd1b.png)
![](https://img.xkw.com/dksih/QBM/2016/11/3/1573122021203968/1573122027552768/STEM/12e37980b7ba49c386e1e3ec94696e78.png)
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|
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4 . 已知数列
,
的通项公式分别为
,
,又
.
(I) 求证数列
是等比数列;
(II) 求数列
的前
项和为
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/606e55241a2e145d54849129b8ffd20f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/039271f3111b0e21bc1282fcc22cf016.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e4b5779873cb3f4366dbfdb983dec81.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b933d363f5b85a6b4110c9ef030c56a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac07953530e3c248b3438fb200fb1661.png)
(I) 求证数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c84bc401cb7e5a4b0bc1157e5dbd194.png)
(II) 求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c84bc401cb7e5a4b0bc1157e5dbd194.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6f18f2c2ec67b5e59e4b3d28795d125.png)
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名校
5 . 已知等比数列
的公比为正数,且
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7999465d0e871febde66296a0cbf058c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4be2164a2c67d6163faee87a10942bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5718641b85fa0d3a1cc48b63dca1d532.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7999465d0e871febde66296a0cbf058c.png)
A.![]() | B.1 | C.2 | D.![]() |
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6 . 已知等比数列
的公比为正数,且
,
,则![](https://img.xkw.com/dksih/QBM/2014/2/28/1571537671028736/1571537676541952/STEM/2dfac59993cd4dc19094289cbfe2db56.png)
![](https://img.xkw.com/dksih/QBM/2014/2/28/1571537671028736/1571537676541952/STEM/bdce0c257dc441f1bac8d7fdf908d6e1.png)
![](https://img.xkw.com/dksih/QBM/2014/2/28/1571537671028736/1571537676541952/STEM/d677a9f317a9445cbdd15ba8c48a0ceb.png)
![](https://img.xkw.com/dksih/QBM/2014/2/28/1571537671028736/1571537676541952/STEM/835859d0333644f2b05d49dfc4f51c2b.png)
![](https://img.xkw.com/dksih/QBM/2014/2/28/1571537671028736/1571537676541952/STEM/2dfac59993cd4dc19094289cbfe2db56.png)
A.![]() | B.![]() | C.2 | D.![]() |
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2011·河北衡水·三模
7 . 等差数列
的前n项和为
,且9
,3
,
成等比数列. 若
=3,则
=
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4be2164a2c67d6163faee87a10942bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e88093a749c0d46e0ee931ecfaff925.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c1ccc6c74b8754e9bcbb3f39a11b6f1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f30f56664446f32dbbc2c5f12a99374.png)
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名校
8 . 若等比数列
的首项是
,且
,则公比等于______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf31876698721a199c7c53c6b320aa86.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0c3f22d8db4b71bd28c58b1b5791ed4.png)
![](https://img.xkw.com/dksih/QBM/2016/1/15/1572439533133824/1572439539105792/STEM/b0486825e58b4e8ba9c7b435936cc4f2.png?resizew=2)
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9 . 设
是等差数列
的前n项和,且
成等比数列,则
等于
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4be2164a2c67d6163faee87a10942bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f8aa010f7105f3ca426c8a34880abd2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34fb3b69403fe5307601f073d8b271a5.png)
A.1 | B.1或2 | C.1或3 | D.3 |
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10 . 在正项等比数列
中,前
项和为
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/614306cc3f34bdee4d5d885b79667645.png)
________ .
![](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/cf2c5c380d738f6c596cfc2db7dc5e78.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/614306cc3f34bdee4d5d885b79667645.png)
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