1 . 在等差数列
中,
为其前
项和.若
,且
,则
等于( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72232ba79bfbce069981786a5462d3e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d37c95cfc939706fee7059af463471e2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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2020-05-09更新
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498次组卷
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6卷引用:2020届湖南省长沙市长郡中学高三月考(三)数学理科试题
2020届湖南省长沙市长郡中学高三月考(三)数学理科试题河北省2019-2020学年高三下学期名优校联考数学(理)试题(已下线)理科数学-6月大数据精选模拟卷01(新课标Ⅰ卷)(满分冲刺篇)(已下线)文科数学-6月大数据精选模拟卷01(新课标Ⅰ卷)(满分冲刺篇)山西省长治市第二中学校2021-2022学年高二上学期第二次月考数学试题重庆市铜梁中学2021-2022学年高二上学期第三次月考数学试题
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解题方法
2 . 已知单调递减数列
的前
项和为
,且
,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1bd9e5d3d9be98c5862934c35306bf01.png)
(1)求![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a82523f6e66a1fa63cae04aa8144c42e.png)
(2)求
![](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/677c103bf88678449276b8944de2fec1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1bd9e5d3d9be98c5862934c35306bf01.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a82523f6e66a1fa63cae04aa8144c42e.png)
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba886db7e66d4161aee2643d1575ab41.png)
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