设
为等差数列
的前n项和,且
,该数列的首项
等于_________ .
![](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/6716319a61ae38e6d6b4e4756775662a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
20-21高三上·广东揭阳·期中 查看更多[3]
广东省普宁市2020届高三上学期期中数学(文)试题(已下线)4.2.3 等差数列的前n项和(课堂培优)-2021-2022学年高二数学课后培优练(苏教版2019选择性必修第一册)(已下线)第02讲 等差数列-【帮课堂】2021-2022学年高二数学同步精品讲义(苏教版2019选择性必修第一册)
更新时间:2021-08-31 23:42:59
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【推荐1】若等差数列
前
项的和为
,且
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c98c59cd4749afdd21e73529fc84323.png)
________
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8d02ea8c4988c5c28ab93f0d70fb55a.png)
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【推荐2】已知数列
是等差数列,
是其前n项和.若
,则
的通项公式![](https://staticzujuan.xkw.com/quesimg/Upload/formula/af93a69f9b370cd469ea70f346a293a9.png)
_______
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f8fade1f573f04f25b9ac5df768400d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b291804cfa1789824686825b6e90be8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/606e55241a2e145d54849129b8ffd20f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/af93a69f9b370cd469ea70f346a293a9.png)
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