题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030704-52843.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030704-61338.png)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030704-52843.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030704-16096.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030704-20380.png)
(2)记
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030705-78282.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030705-53577.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030704-16096.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030705-20336.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030706-42231.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030706-24838.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030704-16096.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030706-30272.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030707-19306.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030704-16096.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030707-79768.png)
解析
试题分析: (1)按照等比数列的定义即可求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030706-42231.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030707-24197.png)
(2)根据(1)结果先求出
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030707-31721.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030707-19306.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030707-79780.png)
(1)设等比数列
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030708-98638.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030708-33887.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030708-44559.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030709-63112.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030709-20055.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030709-52267.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030709-56706.png)
∴ 数列
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030709-37449.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030706-24838.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030706-30272.png)
(2)依题意,由(1)知
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030707-31721.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030710-19046.png)
由裂项相消法得
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030707-79768.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030647-78339.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030648-32133.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030640-37079.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030622-51343.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030622-46163.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030622-48396.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030622-42552.png)
A.4 | B.2 | C.1 | D.-2 |
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030616-50452.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030603-64317.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030603-96925.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030604-24365.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015030604-39929.png)
A.![]() | B.73 | C.![]() | D.15 |
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