已知数列
,若数列
的前
项和
,则
的值为________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e63945bbd2ace9a43cc90a4d6488d2a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/47d4f22f6cf148f50bf15ccfd964f87f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f65fc200f10b97588a0c9896277c9c64.png)
2019·河北·高考模拟 查看更多[3]
(已下线)【全国百强校】河北省衡水中学2019届高三第一次摸底考试数学(理)试题【全国百强校】西藏自治区拉萨中学2019届高三第五次月考数学(理)试题甘肃省武威第六中学2020届高三下学期第二次诊断考试数学(理)试题
更新时间:2019-01-21 18:42:00
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【知识点】 前n项和与通项关系
相似题推荐
填空题-单空题
|
较易
(0.85)
【推荐1】设数列
的前
项和为
,关于数列
有下列三个命题:
①若
即是等差数列,又是等比数列,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32b4e8d0344d6c37a14fc4bdcbf2d992.png)
②若
,则
是等差数列;
③若
,则
是等比数列
这些命题中,真命题的序号是_____________ .
![](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/83cf38189d5cbf627d2b82ac0eb76006.png)
①若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32b4e8d0344d6c37a14fc4bdcbf2d992.png)
②若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a5efc1a32def663934453970ea1e0a37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
③若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7e44407c862e2fe10d79c22a16261db8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
这些命题中,真命题的序号是
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