名校
1 . 已知等差数列
中,
,则数列前9项和
最大值是________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32e572a65f80ea5b548b6f72b1110a8a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05201ef79a5d5904f492845396fb5470.png)
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2 . 已知数列
为等差数列,其前
项和为
,若
(
且
),有以下结论:①
;②
;③
为递增数列;④
.则正确的结论的个数为
![](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/499b0047572a78f286cab0c569447c17.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36b98ef143f8159f3a7dafa1fd2f2370.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a3b59acccb7bb76ced518b36426b7c1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/99ca47be5a21ea60ebd04dd8945852d8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4bd67cf18bd35149475d35f1c603ad59.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78a4e5816786e0db9b85a123f64bfb21.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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