题目内容
(本小题满分12分)
数列
为等差数列,
为正整数,其前
项和为
,数列
为等比数列,且
,数列
是公比为64的等比数列,
。
(1)求
;
(2)求证
。
数列
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134610998263.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611013212.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611044192.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611060220.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611076263.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611091427.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611107385.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611122434.gif)
(1)求
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611138368.gif)
(2)求证
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611154657.gif)
(1)![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611169735.gif)
(2)证明见解析。
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611169735.gif)
(2)证明见解析。
(1)设
的公差为
,
的公比为
,则
为正整数,
,![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611278401.gif)
依题意有
①
由
知
为正有理数,故
为
的因子
之一,
解①得![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611528441.gif)
故![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611169735.gif)
(2)![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611559735.gif)
∴![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231346115751207.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611590971.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611606785.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134610998263.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611200210.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611076263.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611232199.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611200210.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611263512.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611278401.gif)
依题意有
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231346113881566.gif)
由
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611403508.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611232199.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611434198.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611481198.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611512291.gif)
解①得
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611528441.gif)
故
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611169735.gif)
(2)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611559735.gif)
∴
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231346115751207.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611590971.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823134611606785.gif)
![](http://thumb.zyjl.cn/images/loading.gif)
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