记
为等差数列
的前
项和,已知
,
,则
( )
![](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/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc7a6e0d318ebd5dd675c8b53835741b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b5d9cd723a162ac33b06d1869bbd9cb5.png)
A.10 | B.11 | C.12 | D.13 |
更新时间:2020-02-12 22:37:43
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【推荐2】记
为等差数列
的前
项和.若
,
,则
的公差为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/606e55241a2e145d54849129b8ffd20f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6cb15c79e32c2fb6f7d8862885907c4a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e26faf2d524402fefa06823506d1971.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/606e55241a2e145d54849129b8ffd20f.png)
A.1 | B.2 |
C.4 | D.8 |
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【推荐1】已知等差数列
的前n项和为S,
,
,则公差
( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/265ae7f9de1c743deccdf2d30359da21.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6df1038200f2d97a52c716aab6c3bcb6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1aed322d5e349dacab0a9c35f810276.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c98c59cd4749afdd21e73529fc84323.png)
A.-4 | B.-3 | C.3 | D.4 |
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解题方法
【推荐2】在海昏侯墓中发掘出堆积如山的“汉五铢”铜钱.汉代串铜钱的丝绳或麻绳叫“缗”,后来演变为计量铜钱的单位,1000枚铜钱用缗串起来,就叫一缗.假设把2000余缗铜钱放在一起码成一堆,摆放规则如下:底部并排码放70缗,然后一层一层往上码,每层递减一缗,最上面一层为31缗,则这一堆铜钱的数量为( )
A.![]() | B.![]() | C.![]() | D.![]() |
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