题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002716-86487.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002716-92878.png)
(Ⅰ)证明数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002716-32253.png)
(Ⅱ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002716-86487.png)
(Ⅲ)设
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002716-27258.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002716-64480.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002717-50093.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002717-79617.png)
答案
解析
试题分析:
解:(Ⅰ)由已知可得
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002717-51935.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002717-88498.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002718-79484.png)
∴数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002716-32253.png)
(Ⅱ)由(Ⅰ)可得
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002718-35546.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002718-60918.png)
(Ⅲ)由(Ⅱ)知,
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002719-76301.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002719-60619.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002719-86329.png)
相减得
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002719-63615.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002720-44355.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002720-13447.png)
点评:
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002626-77228.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002627-14150.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002627-99788.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002627-90261.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002628-52973.png)
A.18 | B.36 | C.45 | D.60 |
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002459-99496.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002459-32976.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002459-26748.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002500-58019.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002500-22271.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002500-84563.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002459-26748.png)
A.![]() | B.![]() | C.![]() | D.![]() |
(1)已知①a=1、b=2、c=4,试计算
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002451-83207.png)
②a=-1、b=
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002451-25855.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002451-78936.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002451-83207.png)
(2)试推测
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002451-83207.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002326-38916.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002326-54218.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002326-30034.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002327-91688.png)
(2)已知等比数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002327-83026.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010002327-33569.png)
A.10 | B.16 | C.20 | D.32 |
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