题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003014-28856.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003014-84670.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003014-76462.gif)
(1)求数列{
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003014-28856.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003014-28856.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003014-99821.gif)
答案
(1)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003014-28856.gif)
(2)-18
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003015-37476.gif)
得
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003015-91828.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003014-28856.gif)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003015-31759.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003015-93856.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003015-27056.gif)
((2)另解:设前n项的和取得最小,则
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003016-32613.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003016-56875.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003016-78767.gif)
得
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003016-72782.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003015-93856.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003015-27056.gif)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003006-79558.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003006-87694.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013003006-31677.gif)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002956-10329.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002956-10329.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002956-16849.gif)
1
2 2
3 4 3
4 7 7 4
5 11 14 11 5
6 16 25 25 16 6
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002943-55858.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002943-62700.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002944-46554.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002944-49652.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002944-35138.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002944-18066.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002945-37722.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002945-88382.gif)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002943-55858.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002944-35138.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002945-91191.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002945-75851.gif)
(2) 设
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002946-39796.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002946-98651.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002946-57855.gif)
(3) 设
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002946-75535.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002945-88382.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002946-36861.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002947-77247.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002933-27370.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002933-29068.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002933-27370.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002920-20670.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013002920-20670.gif)
A.![]() | B.5 | C.2 | D.![]() |
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