已知等差数列
的前
项和为
,
,
与
的等差中项为2,则
的值为( )
![](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/c98042df89eacc7ce1013c7ab1e5af35.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e88093a749c0d46e0ee931ecfaff925.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/daf464629fa321a6ff7401ab79f07083.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f30f56664446f32dbbc2c5f12a99374.png)
A.6 | B.-2 | C.-2或6 | D.以上都不对 |
更新时间:2021-10-14 16:57:44
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【推荐2】在等差数列
中,已知
与
的等差中项是
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a7bf78468ca801ef305ce4f76986da1.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
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A.![]() | B.![]() | C.![]() | D.![]() |
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【推荐1】已知等差数列
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a91c96b09ea8d935e484410742943615.png)
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【推荐2】若实数
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/040328863cb2c5b2e54336fde43643fd.png)
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【推荐1】已知等差数列
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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【推荐2】已知等差数列
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