题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073918-28122.png)
(1)求数列{an}的通项公式;
(2)求前n项和
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073918-90778.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073918-51013.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073919-36047.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073919-23266.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073918-90778.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073919-34807.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073919-19761.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073920-51192.png)
(2)利用二次函数的性质,求出对称轴为
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073920-43636.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073930-31055.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073930-30084.png)
(1) 当
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073931-38979.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073931-98048.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073931-36866.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073931-64684.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073931-38979.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073931-26565.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073919-36047.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073932-21233.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073930-31055.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073930-30084.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073918-90778.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073919-34807.png)
核心考点
举一反三
己知数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073856-29323.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073856-58553.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073856-93677.png)
(1)求证:数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073857-34339.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073857-83896.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073857-58229.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073908-93814.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073908-81553.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073909-72158.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073643-89471.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073649-14283.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073649-80948.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073649-73425.png)
A.1 | B.2 | C.3 | D.4 |
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073633-59313.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073607-99821.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073607-90497.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073608-67942.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073608-32074.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073520-93899.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073520-36082.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073521-85990.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073521-64062.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073521-74114.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073521-24191.png)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073520-93899.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073521-64062.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073522-37948.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073522-12982.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073522-51756.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010073522-38537.png)
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