题目内容
若
且
,则
的取值范围是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703257534.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703272613.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703288570.png)
A.![]() | B.![]() | C.![]() | D.![]() |
A
本题考查函数思想和转化思想及二次函数的性质.
含有两个变量的问题常用一个变量表示另一个变量代入消去一个变量,转化为函数问题.
由
得
;于是
;又
解得
设
二次函数
在
上是减函数,在
上是增函数;
所以函数
的值域为
即为
的取值范围.故选A
含有两个变量的问题常用一个变量表示另一个变量代入消去一个变量,转化为函数问题.
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703366596.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703381582.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231907033971011.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703413677.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703428519.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231907034591410.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703475447.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703491516.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703506500.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231907035221110.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703475447.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703553506.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823190703569549.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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