已知等差数列
中,前四项的和为
,最后四项的和为
,且前
项和
,则
为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b3779b4ea5477aebfe85113b0de1d60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f534536cc2ccc32cc535e6a5561f99a1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bec2cf9b2b15dadbf85bb506f162d329.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7fd71bc7e6668f90f259ad0b06dd60c2.png)
A.![]() | B.![]() | C.![]() | D.![]() |
更新时间:2021-03-26 16:17:31
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【推荐1】已知数列
是各项均为正整数的等差数列,记
是
的前
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
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A.2022 | B.2023 | C.4049 | D.4054 |
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【推荐2】已知在等差数列
中,
,则
( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/69b7d1b0e84b27de77f11bdb3096ea9c.png)
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A.4 | B.6 | C.8 | D.10 |
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解题方法
【推荐1】已知等差数列
的前
项和为
,若
,则
( )
![](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/f18bb265fde0ead55c8eef46aa2ee66a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9eab8f8926b996f9bee57d96067f5bac.png)
A.36 | B.48 | C.96 | D.24 |
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【推荐2】已知公差不为零的等差数列
满足
,
为数列
的前n项和,则
的值为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d376f4c1086e3949599004acfca90e27.png)
![](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/65fb94243b98766241d945fd8d861b92.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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