1 . 数列
是等差数列,若
,
,
则使前
项和
成立的最大自然数
是________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/390636a89883bd64bf8da9bf8654aff9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/53d060e2604af6990cdd6bf844fba2a0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f836a93dfcd214164876df36de0f0e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49763402b2f2023f0ba64c37924267d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
您最近一年使用:0次
2020·全国·一模
名校
解题方法
2 . 已知
,
是椭圆
:
的左、右焦点,过
的直线交椭圆于
两点.若
依次构成等差数列,且
,则椭圆
的离心率为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5076289823db419f94e9c0c8f4aafd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3fb78c5f885034612c0e030b920143d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e9b03b8e79f17b27f7dc5f5ee2e11f71.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3fb78c5f885034612c0e030b920143d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6bce3d91ca23b86d8c6625f2632e437.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fb965dc10bf87847bbff5c6246b3ab3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b48868841f12f3213f8412a1afb1bc28.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
A.![]() | B.![]() | C.![]() | D.![]() |
您最近一年使用:0次
2020-04-02更新
|
560次组卷
|
6卷引用:2020届宁夏六盘山高级中学高三下学期第一次模拟考试数学(理)试题
2020届宁夏六盘山高级中学高三下学期第一次模拟考试数学(理)试题(已下线)学科网3月第一次在线大联考(新课标Ⅰ)数学(理科)试题江西省抚州市临川第一中学2019-2020学年高三5月模拟考试数学(理)试题(已下线)理科数学-学科网3月第一次在线大联考(新课标Ⅰ卷)(已下线)理科数学-学科网3月第一次在线大联考(新课标Ⅱ卷)安徽省芜湖市第一中学2020届高三下学期3月第五次线上考试数学试题
3 . 设等差数列
的前
项和为
,已知
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc4e70b360f988fdbd92300ab22c4613.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d737c1047a14cee12a6671383e244fa5.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/0050d6a0715d206941762b1d54baa397.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc4e70b360f988fdbd92300ab22c4613.png)
A.-27 | B.27 | C.-54 | D.54 |
您最近一年使用:0次
2016-12-04更新
|
834次组卷
|
6卷引用:2016届宁夏六盘山高中高三第三次模拟考试文科数学试卷