在等差数列
,
,
,
,…中,
(1)求前20项的和;
(2)已知前n项的和为
,求n的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5e6486784415f3537c9a13556c05d893.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4dac452fbb5ef6dd653e7fbbef639484.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf31876698721a199c7c53c6b320aa86.png)
(1)求前20项的和;
(2)已知前n项的和为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b424b97a443e0032e946fef0f16b3751.png)
21-22高二·江苏·课后作业 查看更多[2]
更新时间:2022-02-28 21:22:34
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解答题-问答题
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【推荐1】在等差数列
中,已知
,
.
(1)求数列
的通项公式;
(2)若数列
的前n项和为
,且
,求m的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fdc215481b2f2574d70718472f41a321.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)若数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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【推荐1】在①
,②
③
这三个条件中任选,补充在下面的问题中.
问题:已知
为等差数列,设其前n项和为
,___________,是否存在正整数m,k(其中
),使得
.成立?若存在,写出m,k满足的关系式;若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4a83d3c96529415d15d9ef03f80aa5b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f80f08180179c821d30983f2950347b.png)
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问题:已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b66a3969de120b50c1c2643a89629ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0942a9ad4f1a3bf81b58d760bd9e7a86.png)
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您最近一年使用:0次
解答题-问答题
|
较易
(0.85)
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【推荐2】已知等差数列
的前
项和为
,
,
.
(1)求
的通项公式;
(2)求
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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/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65c42652d6d36a308c8d1a139fd56354.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a04747e6fbdfdec7db1909e1b112088d.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
您最近一年使用:0次