已知各项均不相等的等差数列
的前5项和为30,且
,
,
是等比数列
的前3项.
(1)求
,
.
(2)设数列
的前
项和为
,
,求数列
的前6项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.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/daf464629fa321a6ff7401ab79f07083.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/686ece75006ad358f23314dc8a246e11.png)
(2)设数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.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/96b96ad5c632cda5732ab35b1b7e8286.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57ef6d44448092ebdb9e4a49d866a749.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a9b647ac8a8174071a4f332a00b5507b.png)
更新时间:2020-12-16 22:05:10
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解答题-问答题
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适中
(0.65)
名校
解题方法
【推荐1】已知
为等差数列
的前
项和,且满足
,
.
(1)求
的通项公式;
(2)求
的最大值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.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/d353bbb188aeb859fd8ae194871e8d50.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee7f18ec0020048985d101969880d93e.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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【推荐2】已知等差数列
的前
项的和为
,公差
,若
,
,
成等比数列,
;数列
满足:对于任意的
,等式
都成立.
(1)求数列
的通项公式;
(2)证明:数列
是等比数列;
(3)若数列
满足
,试问是否存在正整数
,
(其中
),使
,
,
成等比数列?若存在,求出所有满足条件的数组
;若不存在,请说明理由.
![](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/4dd71318ddbb81a2d7ed7847e1ff744a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d199f9235e3bd36bfa78c3772e941896.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05c2f981c2c9d55dbea8172ff5ccf0db.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e86dd1bbf78bf258d2a235bb624877f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dcc76e978ba70adffee6b6737c4b15d6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2448cf72af76b810310e4cfb9818e2e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb8c29b297e3ec337c3139c2a1ebed1b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6468f6b102bab3f13acba779db533a24.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29518f13a1ebc3fff8181c2d7cfba22f.png)
(2)证明:数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2448cf72af76b810310e4cfb9818e2e.png)
(3)若数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4a426d8afd49a1ce1e8dddd2ea37498.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b247421f7c273aaca1813a7efb0d392.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5873c01192b7d33b7483f444f90b5b0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/67582f5e747aa312cf4c16eb5da4f165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6421ab6a8c25fdfd76167df1b5054127.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8aa96bb93470076b012d0680a831ac2e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/56e39e9fe7f8f0b4f18ac4081f4b6f2e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aa6d32a978500d09be2ed262fca2f242.png)
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【推荐1】设等差数列
的前n项和为
,且
,
.
(1)求数列
的通项公式;
(2)求数列
的前n项和
.
![](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/f87021fd95fddc7dd54318cb2a235edc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a889e13ba8518fa34494ed1295078999.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4be2164a2c67d6163faee87a10942bb.png)
(2)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ff54c8b3756dc6feea568be0fa70e9b8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
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适中
(0.65)
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解题方法
【推荐1】已知
为等比数列,且
,
成等差数列.
(1)求数列
的通项公式;
(2)当
为递增数列时,
,数列
的前
项和为
,若存在
,求
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b932ddacaf5235694da0d7313cbcf65c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d5bf63073229c4be28e2d364158b9e4e.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3efb35242a402f56ffb3bcb42c1fbce5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fce83115a50f99e08e9a2db7267aeed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccb1a48a676bf1f56f4209e2b37721c6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
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【推荐2】设
为正项数列
的前
项和,且满足
.
(1)求证:
为等差数列;
(2)令
,
,若
恒成立,求实数
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.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/b61cc942eaa2c2d9f47608ddfcdd716c.png)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)令
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/216876de04325fd250c38c485cbc34b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd597fd3e8cf7d5fb0de8c0f18bd785c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4926941ae3d14b022fabbb840095aedb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
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