名校
解题方法
1 . 已知无穷等比数列
的首项是
,公比为
,这个数列的前
项和总是大于这个数列的各项和,那么下列结论正确的是( )
![](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/9aa8a716a31b0f51b70fdf9bdb257909.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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名校
2 . 设
为数列
前
项的和,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c7c64e93b4e092dc6b3d4fc4393bb35.png)
,数列
的通项公式![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c86951c02fc7ae8598c09f69ad585eb.png)
.
(1)求数列
的通项公式;
(2)若
,则称
为数列
与
的公共项,将数列
与
的公共项,按它们在原数列中的先后顺序排成一个新数列
,求
的值;
(3)是否存在正整数
、
、![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
使得
成立,若存在,求出
、
、
;若不存在,说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d3cfeacc29e6a61c5b3b4e439c0a91df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c7c64e93b4e092dc6b3d4fc4393bb35.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf6e5629ab1d2ed93025a91df8e4c9d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fce83115a50f99e08e9a2db7267aeed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c86951c02fc7ae8598c09f69ad585eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf6e5629ab1d2ed93025a91df8e4c9d4.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d369e93e80d14de80311d1984572f787.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c02bc0c74292b1e8f395f90935d3174.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fce83115a50f99e08e9a2db7267aeed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fce83115a50f99e08e9a2db7267aeed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d813f3ca8db41a4db6c18eac30fef98.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c8323971c280d065008036a42b94cd74.png)
(3)是否存在正整数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11bc05f41215f9894e11d1df0465751a.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/0bf956c1aab257331cafa8d2d4ddcb71.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24dd1ec3d1b75b0e49599eb6416d5126.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11bc05f41215f9894e11d1df0465751a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5873c01192b7d33b7483f444f90b5b0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
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