在等差数列
中,
,
.记数列
的前
项和为
.
(1)求
;
(2)设数列
的前
项和为
,若
成等比数列,求
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/28d84ee688592caf22e84910db79e7d0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/567774c568238bc2553d4b122eff8ea4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e575361303595eb25710553337bb2708.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
(2)设数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65fb925837d7fb964b093ca501c16ee9.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/54f61fbefedec7a6ff00d1e188096630.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7e74be91bfe4bc209da7539dbf9b72c.png)
更新时间:2017-12-07 13:57:29
|
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【推荐1】已知数列
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解答题-问答题
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适中
(0.65)
解题方法
【推荐2】设正项数列
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![](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/ae734ad099abbb2f7efe7d7a6a4169fd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/995b6df46545eb47cd0224ddc1e7bb21.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4618ab59ce7f457dc9d583a5cdb42330.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
您最近一年使用:0次