已知
是等差数列
的前n项和,若
,
,则
=______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fa561fcad46eaf8d841efa58fe9a8af2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49889abfa24edb862e45a44329a904f4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32e096395cf359ca14d80bef3ea199ba.png)
22-23高二上·黑龙江哈尔滨·期中 查看更多[3]
更新时间:2022-12-01 21:21:06
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填空题-单空题
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适中
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解题方法
【推荐1】已知抛物线E:y2=4x,A(x1,y1),B(x2,y2),C(x3,y3)为抛物线上的三个动点,其中x1<x2<x3且y2<0,若
ABC的重心恰为抛物线E的焦点,且AB、AC、BC三边中点到抛物线E的准线的距离成等差数列,则直线AC的斜率为_____ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce4cba95fc7d4853a243f8e3fb20ce70.png)
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解题方法
【推荐2】设数列
的前
项和为
,若
成等差数列,且
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42e4487468ab2823d6dbf7f0ebd2eb38.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/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7191cd21332e8c6e07941f877802d683.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3299d1d394efc1381671b1632e6e87e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42e4487468ab2823d6dbf7f0ebd2eb38.png)
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【推荐1】【2018届上海市十二校高三联考】 若等差数列
的前5项和为25,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fbfc875ca919921e8f63a6fca648561b.png)
________
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fbfc875ca919921e8f63a6fca648561b.png)
您最近一年使用:0次
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【推荐2】给出下列四个命题:
①函数
的最小值是2;
②等差数列
的前n项和为
,满足
,
,则当
时,
取最大值;
③等比数列
的前n项和为
,若
,
,则
;
④
,
恒成立,则实数a的取值范围是
.
其中所有正确命题的序号是________________________ .
①函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04d70d0e3ed9ec29c36ff3ef8ed70676.png)
②等差数列
![](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/7df7fe8cd58a89cef831601f361c6c23.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ee92298a0a93de40f051e1bfbafdb95.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e45cf86650443d1b86c79b1e3edc7e5c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
③等比数列
![](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/8c9b5080aa2e9c889aac8e378d83dfee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/38db0637b08ba3fb6a230f8e08ba438f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f3fe9c754ea5c056751fe63ea196fbf5.png)
④
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c780149aef1bd77162e85f7f8906a6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/234238ab6e84426626828d5fc73a2d81.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c880a292e77ec85d531c1b37e6feffe6.png)
其中所有正确命题的序号是
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