题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000935-61031.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000935-41015.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000936-39199.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000936-70712.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000936-91422.gif)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000936-34397.gif)
(2)记
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000937-42457.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000936-91422.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000937-25409.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000937-73116.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000937-30277.gif)
答案
(1)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000937-54174.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000936-91422.gif)
(2)对任意正整数n,都有
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000937-30277.gif)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000938-28115.gif)
当n = 1时,
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000938-44946.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000938-91561.gif)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000938-82772.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000939-84884.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000939-35446.gif)
∴数列
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000935-61031.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000938-91561.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000939-24262.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000939-76392.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000937-54174.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000936-91422.gif)
(2) 由(1)知
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000940-71192.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000940-43466.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000940-30780.gif)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000940-16354.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000941-53273.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000941-64726.gif)
当n = 1时,
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000941-40341.gif)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000938-82772.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000941-79678.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000941-92209.gif)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000916-49480.gif)
A.4 | B.2 | C.1 | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000844-60507.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000844-34296.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000844-79097.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000845-17885.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000840-27326.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000840-55496.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000840-39250.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000840-37057.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000840-39250.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000840-39250.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000832-57327.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000832-72331.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000833-20624.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000832-72331.gif)
n等于( )
A.6 | B.7 | C.8 | D.9 |
已知数列
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000826-76731.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000827-29096.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000827-75901.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000826-76731.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000827-23624.gif)
①若
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000827-75901.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000827-29096.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000826-76731.gif)
②
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000827-25243.gif)
③若
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000826-76731.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000827-48557.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000828-60111.gif)
④若
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000826-76731.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000828-79630.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000828-23581.gif)
⑤若
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000826-76731.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191013/20191013000828-65533.gif)
A.2 | B.3 | C.4 | D.5 |
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