题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-62410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-99410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-42110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-38822.png)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-62410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-99410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-29510.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-42110.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-64003.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-89729.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111610-70054.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-62410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-99410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111610-58216.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-29510.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111610-85793.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111610-50346.png)
解:(1)因为数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-62410.png)
所以数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-62410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-64003.png)
因为数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-99410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-42110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-38822.png)
所以当
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111611-19487.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111611-42733.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111611-54113.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111611-59088.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111611-15257.png)
所以数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-99410.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-89729.png)
(2)由(1)可知,
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111611-91890.png)
设数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-29510.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-42110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111612-55671.png)
则
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111610-85793.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111610-50346.png)
①-②,得
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111612-71479.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111612-19589.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111612-87839.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111613-74418.png)
故数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111609-29510.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111608-42110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111610-70054.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111535-58764.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111535-75507.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111535-13852.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111452-63676.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111453-36355.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111453-44672.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111436-77857.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111436-78984.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111431-13640.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111431-18091.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111431-48890.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111431-38719.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111417-90523.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111417-90523.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111417-50013.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111417-33584.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012111417-59752.png)
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