题目
题型:不详难度:来源:
数列
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094028-11750.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094028-62217.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094029-53010.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094029-24112.gif)
(Ⅰ)证明:数列
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094029-98483.gif)
(Ⅱ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094028-11750.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094029-47317.gif)
(Ⅲ)设
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094030-28027.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094030-85558.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094030-72046.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094030-84411.gif)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094030-84514.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094031-83811.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094031-69443.gif)
∴ 数列
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094029-98483.gif)
(Ⅱ)由(Ⅰ)知
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094031-97715.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094031-92591.gif)
(Ⅲ)由(Ⅱ)知
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094031-93218.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094032-93007.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094032-35132.gif)
相减得:
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094032-21592.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094032-52659.gif)
解析
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094023-41943.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094023-12934.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094023-56562.gif)
A.![]() | B.![]() ![]() | C.![]() | D.1 |
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094017-26158.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094018-28994.gif)
A.![]() | B.![]() | C.2 | D.5 |
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094002-58234.gif)
a、b、c成等比数
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094002-74929.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094002-38709.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094003-84616.gif)
A.2:1 B.
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094003-21438.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011094003-52756.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011093933-45564.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011093934-70370.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011093934-53358.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011093934-31396.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011093919-39761.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011093919-88123.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191011/20191011093919-88927.gif)
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