题目内容
已知数列
满足
,
(
且
)
(Ⅰ)证明数列
是常数列;
(Ⅱ)求数列
的通项公式;
(Ⅲ)当
时,求数列
的前
项和.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184945792263.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184945808435.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184945824629.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184945855243.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184945886368.gif)
(Ⅰ)证明数列
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946120535.gif)
(Ⅱ)求数列
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184945792263.gif)
(Ⅲ)当
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946229482.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184945792263.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946260192.gif)
(Ⅰ)证明:![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946276648.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946292602.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946323944.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946526128.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231849465571045.gif)
即![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946572528.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946588507.gif)
数列
是常数列. …………………………………4分
(Ⅱ)解:![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231849466501549.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946728609.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946526128.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946760727.gif)
……………………………6分
当
时,
是等比数列,首项![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946869429.gif)
,公比![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946900289.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946916687.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946931874.gif)
当
时,
满足上式. ………………………………8分
(Ⅲ)解:![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231849470091071.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947134539.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947165547.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947337557.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231849473521020.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947477716.gif)
………………………………12分
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946276648.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946292602.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946323944.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946526128.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231849465571045.gif)
即
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946572528.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946588507.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946526128.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946635532.gif)
(Ⅱ)解:
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231849466501549.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946728609.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946526128.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946760727.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946822547.gif)
当
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946838264.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946853506.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946869429.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946884287.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946900289.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946916687.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946931874.gif)
当
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946962258.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184946978262.gif)
(Ⅲ)解:
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231849470091071.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947134539.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947165547.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947337557.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231849473521020.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947477716.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823184947493658.gif)
略
![](http://thumb.zyjl.cn/images/loading.gif)
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