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解题方法
1 . 已知首项相等的两个数列
满足
.
(1)求证:数列
是等差数列;
(2)若
,求
的前n项和
;
(3)在(2)的条件下,数列
是否存在不同的三项构成等比数列?如果存在,请你求出所有符合题意的项;若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3749f21ab960f83ced063bf49e0da77.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/948f39334fbedeb849be39552aa00c4c.png)
(1)求证:数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2767882820f4ba0defde0e412adb747f.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7bb72b3ebbca741b3eda49cd617c058.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
(3)在(2)的条件下,数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/846fa57d92d6ad44d6a0cafad1e71ed4.png)
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