题目内容
(本小题满分14分)
已知定义在R上的单调函数
,存在实数
,使得对于任意实数
总有
恒成立.(Ⅰ)求
的值;(Ⅱ)若
,且对任意正整数
,有
,记
,
,比较
与
的大小关系;
(Ⅲ)若不等式
对任意不小于2的正整数
都成立,求
的取值范围.
已知定义在R上的单调函数
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115552857270.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115552904204.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115552920240.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115552967896.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115552904204.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553029336.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553045192.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553076765.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553091634.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553107647.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553138398.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553154211.gif)
(Ⅲ)若不等式
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155531851252.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553045192.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553216187.gif)
(Ⅰ)
(Ⅱ) 略(Ⅲ)
或![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553325339.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553232247.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553263387.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553325339.gif)
(Ⅰ)令
,得
①
令
,得
②
由①,②得
为单调函数,∴
.
(Ⅱ)由(Ⅰ)得
,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553591974.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553669637.gif)
,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553825504.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553856931.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553887875.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553934574.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155539961791.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155540271390.gif)
,
(Ⅲ)令
,
则
∴当
时,![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155541521005.gif)
即![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115554168839.gif)
解得
或![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553325339.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553341310.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553388916.gif)
令
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553435337.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155534501010.gif)
由①,②得
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553466412.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553481298.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553232247.gif)
(Ⅱ)由(Ⅰ)得
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155535131101.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553591974.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553622490.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553637486.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553653947.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553669637.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155537001515.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553778933.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553825504.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553856931.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553887875.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553934574.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155539961791.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115554012969.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155540271390.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155540431416.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155540591089.gif)
(Ⅲ)令
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115554090624.gif)
则
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155541051573.gif)
∴当
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115554121464.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155541521005.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408231155541521107.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115554168839.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115554183948.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553263387.gif)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823115553325339.gif)
![](http://thumb.zyjl.cn/images/loading.gif)
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