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解题方法
1 . 在等差数列
中,
是其前n项和,已知
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc4e70b360f988fdbd92300ab22c4613.png)
___________ .
![](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/c705ed1d40eb3d40ebadd05dbb645b73.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b0f26b164343313555807c8de790aa7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc4e70b360f988fdbd92300ab22c4613.png)
您最近一年使用:0次
2023-09-13更新
|
749次组卷
|
6卷引用:甘肃省临夏州临夏中学2021-2022学年高二上学期期中(文科)数学试卷(b卷)
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2 . 已知数列
是一个等差数列,
,公差
,则其首项
( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb334e165679c6cb500c994cffa47147.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3e2f2e4ec975aabd9fc243499cbb49e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7999465d0e871febde66296a0cbf058c.png)
A.3 | B.4 | C.5 | D.6 |
您最近一年使用:0次
2023-09-13更新
|
866次组卷
|
3卷引用:甘肃省临夏州临夏中学2021-2022学年高二上学期期中(文科)数学试卷(b卷)
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3 . 由
,
确定的等差数列
,当
时,n等于___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f2572192cc7ca046e9a3155ef3e56a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b03f2bcba30e02f05baea750ac4a8e0.png)
您最近一年使用:0次
4 . 等差数列
中,
,
.
(1)求
;
(2)若这个数列的前n项和为
,求
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/232faf3b3aa63b4708168a3883dc2ec3.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7fd71bc7e6668f90f259ad0b06dd60c2.png)
(2)若这个数列的前n项和为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/194592cb77de8a597d5d64e1c85c3249.png)
您最近一年使用:0次