记
为等差数列{an}的前n项和.若
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4259345a7b1964a756911dbe0ed9ee42.png)
___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2ef0f4a21029a041976b8d86257e7666.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4259345a7b1964a756911dbe0ed9ee42.png)
更新时间:2021-10-05 21:03:04
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解题方法
【推荐1】已知等差数列
的前n项和为
,
,
,则数列
的前20项和是______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf61dc9e4c4d73e61bda915e8f0814d1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/399e6a6eaf116586241839185593dc3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b91adba8efbf964e9e35547b0fd0ea36.png)
您最近一年使用:0次
填空题-单空题
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【推荐2】设等差数列
的公差
不为0,
,若
是
与
的等比中项,则k等于______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c02bc0c74292b1e8f395f90935d3174.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3507603040778ec586b860215fa3f08b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f255d0395fba51ca2d44293cca42e0a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/39773a450e3c30c72ead226d84e54563.png)
您最近一年使用:0次
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名校
解题方法
【推荐2】设
为等差数列
的前
项和,且
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b2778e2dadff4d91102e6046bb5def8.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/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2ce69f13ac0f2736e2b2a718942c49fd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b2778e2dadff4d91102e6046bb5def8.png)
您最近一年使用:0次