解题方法
1 . 记
为等差数列
的前n项和,已知
,
,
,
的前n项和为
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/681967bfbdcdae96320e06da896b4da4.png)
_________ .
![](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/4ac577f987d768e1a115f2747ec0fd6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3977c8261a26b09c1aa8d1ff87075666.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9ebf05ca12f9da810b2b10e066ececf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/681967bfbdcdae96320e06da896b4da4.png)
您最近一年使用:0次
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2 . 已知数列{an}中,
,
,若
是等差数列,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d211c5a622d0be3b39931d814f9a683.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb334e165679c6cb500c994cffa47147.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/259b2e755105c0ee479eabf7265a76a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f2f41fa38f6cc1c6ded8367cc359b341.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d211c5a622d0be3b39931d814f9a683.png)
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2019-11-10更新
|
224次组卷
|
2卷引用:天津市宁河区芦台第一中学2019-2020学年高二上学期第一次月考数学试题
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3 . 公差大于零的等差数列
中,
,
,
成等比数列,若
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/715aaa320d35fd92b2dcd9573ab8b489.png)
_____________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f65fc200f10b97588a0c9896277c9c64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d33ec7236bccfedbe3baefd35e45f1e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e84c30444f13d37ada78285dc4f83b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1928c254cfada1f75a5cd1e34db5a63.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/715aaa320d35fd92b2dcd9573ab8b489.png)
您最近一年使用:0次