20-21高二·全国·课后作业
解题方法
1 . 已知数列{an}的前n项和为Sn,数列{an}为等差数列,a1=12,d=-2.
(1)求Sn,并画出{Sn}(1≤n≤13)的图象;
(2)分别求{Sn}单调递增、单调递减的n的取值范围,并求{Sn}的最大(或最小)的项;
(3){Sn}有多少项大于零?
(1)求Sn,并画出{Sn}(1≤n≤13)的图象;
(2)分别求{Sn}单调递增、单调递减的n的取值范围,并求{Sn}的最大(或最小)的项;
(3){Sn}有多少项大于零?
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2 . 首项为正数,公差不为
的等差数列
,其前
项和为
.现有下列
个命题,其中是真命题的有( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c95b6be4554f03bf496092f1acdfbb89.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f67fd0eb54561cd1df683a08cf049bfc.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/b8860d9787671b53b1ab68b3d526f5ca.png)
A.若![]() ![]() |
B.若![]() ![]() ![]() ![]() |
C.若![]() ![]() ![]() ![]() |
D.若![]() ![]() |
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4卷引用:江苏省黄桥中学、口岸中学、楚水实验三校联盟2020-2021学年高二上学期期中联考数学试题
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3 . 设等差数列
的前
项和为
,若
,
,则当
取得最大值时,
的值为_______________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.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/390636a89883bd64bf8da9bf8654aff9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8c98614b893bc98ede0f87d4b0a00cfd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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4 . 已知等差数列
的前
项和为
.若
,公差
,则
的最大值为_______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd015442628054692b8cc0a19c77d2bf.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/366dfedff1a1a96ec27650375b680059.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc807ea4b8a7ed325aee49aa292552ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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2020-11-15更新
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7卷引用:北京市海淀区2021届高三上学期期中考数学试题
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5 . 已知无穷等差数列
的前n项和为
,
,且
,则( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fe229b24e2d56ff6b491725ceae4ff2f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b708c8dcb2d66eb2ce0b3718a9cd924a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ae2fb7263931f3bcda16e78db20182ec.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2cf250dad5a16d36a6f388539b69f452.png)
A.在数列![]() ![]() | B.在数列![]() ![]() ![]() |
C.![]() | D.当![]() ![]() |
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解题方法
6 . 已知等差数列{an}的前n项和为Sn,a1+a5=0,a2=2.
(Ⅰ)求数列{an}的通项公式;
(Ⅱ)求Sn的最大值及相应的n的值.
(Ⅰ)求数列{an}的通项公式;
(Ⅱ)求Sn的最大值及相应的n的值.
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解题方法
7 . 已知等差数列
的通项公式为
,则使得前
项和
最小的
的值为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b495d7ca3e7b07badadefeb125111234.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)
A.![]() | B.![]() | C.![]() | D.![]() |
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10-11高一下·四川成都·期中
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8 . 等差数列
的前
项和为
,
,
,则
取最大值时![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f3cb8d72bb2e281b943b3b430138ef7.png)
________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.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/390636a89883bd64bf8da9bf8654aff9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/619ef41442789786a473b6ffa8e73f4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f3cb8d72bb2e281b943b3b430138ef7.png)
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2020-07-15更新
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9 . 在等差数列
中,
为它的前
项和,若
,
,
,则当
最大时,
的值为( ).
![](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/390636a89883bd64bf8da9bf8654aff9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb15e818ed3399e6acfb390f4805b743.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d9f0853863ab2c68e6393b1049aa7fe3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
A.9 | B.10 | C.18 | D.19 |
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10 . 已知等差数列
的前
项和为
,且满足:
,
.
(1)求数列
的通项公式;
(2)记数列
的前
项和为
,求
取得最大值时
的值.
![](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/c01275cebf334efe1639f838efc720c6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/856789e8ef3064cab89d8de2daf6069d.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)记数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4dea1dd4ffcb4cf0697ca43079f6a1f2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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