9-10高一下·广东湛江·期末
1 . 设等差数列
第10项为24,第25项为-21,.
(1)求这个数列的通项公式;
(2)设
为其前
项和,求使
取最大值时的
值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(1)求这个数列的通项公式;
(2)设
![](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/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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9-10高一下·河北邯郸·期末
名校
解题方法
2 . 已知等差数列
中,
为
的前
项和,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f87a281b8d984b3681b3763d7e1446f7.png)
(1)求
的通项
与
;
(2)当
为何值时,
为最大?最大值为多少?
![](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/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f87a281b8d984b3681b3763d7e1446f7.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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9-10高二下·广东广州·期中
解题方法
3 . 设等差数列
的前
项和为
且满足
则
中最大的项为______.
![](https://img.xkw.com/dksih/QBM/2014/5/12/1571704129732608/1571704135090176/STEM/db5ecf28b15a4ead83c13beb68e6dffa.png?resizew=32)
![](https://img.xkw.com/dksih/QBM/2014/5/12/1571704129732608/1571704135090176/STEM/8d51e44cbedc489fa2e86014c19a07a0.png?resizew=13)
![](https://img.xkw.com/dksih/QBM/2014/5/12/1571704129732608/1571704135090176/STEM/c38e12a576374d299f2bfc6bcfb71741.png?resizew=25)
![](https://img.xkw.com/dksih/QBM/2014/5/12/1571704129732608/1571704135090176/STEM/cf79ec6fe2a346cea65b8fa8a1cce530.png?resizew=104)
![](https://img.xkw.com/dksih/QBM/2014/5/12/1571704129732608/1571704135090176/STEM/c9cb80573ddb442eb5a4a77842fef174.png?resizew=91)
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9-10高一下·浙江宁波·期中
4 . 若无穷等差数列
的前
项和为
,且
,
,则
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4be2164a2c67d6163faee87a10942bb.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/6df775bbb96051716b1971fdfc42c210.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5ad422a03467f70121b4a3cd3c724d9.png)
A.在![]() |
B.![]() |
C.![]() |
D.![]() |
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