题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-42233.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-15423.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-59461.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-26822.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091213-78063.png)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-42233.png)
(2)在
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091213-99004.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091213-67511.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091213-96304.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091213-33027.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-15423.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-42054.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-98572.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-54266.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-26822.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-55349.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091215-25856.png)
再两式相减得:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091215-74150.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091215-27146.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-42233.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091215-66110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-42233.png)
(2) 由(1)知
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-98572.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091216-61828.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091217-36928.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091217-54135.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091217-27034.png)
(1)由
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-26822.png)
得
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-55349.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091215-25856.png)
两式相减得:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091215-74150.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091217-33780.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091215-25856.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091212-42233.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091215-66110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091217-56775.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091218-24168.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091218-73981.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-98572.png)
(2)由(1)知
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-98572.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091216-61828.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091217-36928.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091218-73390.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091218-27943.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091218-99598.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091220-30944.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091220-88596.png)
①-②得
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091220-14318.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091220-63177.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091221-94020.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091214-54266.png)
核心考点
试题【(12分)设等比数列的前项和为,已知N).(1)求数列的通项公式;(6分)(2)在与之间插入n个数,使这n+2个数组成公差为的等差数列,求数列的前项和.(6分)】;主要考察你对等差数列等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091200-75743.png)
A.19 | B.10 | C.9 | D.5 |
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091147-64738.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091147-60153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091147-60425.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091147-35782.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091148-41882.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091148-21784.png)
(I)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091148-78677.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091148-75198.png)
(II)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091149-40121.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091149-56738.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091149-81935.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091141-24483.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091141-84875.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091141-36971.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091142-71280.png)
且
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091142-72914.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091142-35483.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091130-51342.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091130-79556.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091130-75510.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091130-62189.png)
A.52 | B.54 | C.56 | D.58 |
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091117-55236.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091117-92360.png)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091117-55236.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091117-55236.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091117-85472.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091117-52398.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091117-69833.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012091118-55732.png)
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