设数列
是首项为1的等差数列,前
项和
,
,则公差为___________ .
![](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/ea5cc09a66cb35ef1ee5fce4dd3da8ca.png)
更新时间:2017-02-08 11:15:24
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【知识点】 等差数列前n项和的基本量计算
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【推荐1】等差数列
的前
项和为
,若
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__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3adf2bf9a573b812ba2039e75368395.png)
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填空题-单空题
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较易
(0.85)
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【推荐2】在等差数列
中,前7项的和
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81e563b8d1da5930696a0e6d17d2d1df.png)
___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9a39dabf1d2cb4094bd2178576970d29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81e563b8d1da5930696a0e6d17d2d1df.png)
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