题目内容
已知f(x)是偶函数,且f(x)在[0,+∞)上是增函数,如果f(ax+1)≤f(x-2)在x∈[
,1]上恒成立,求实数a的取值范围.
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824052525270338.png)
[-2,0]
解:由于f(x)为偶函数,且在[0,+∞)上为增函数,由f(ax+1)≤f(x-2),则|ax+1|≤|x-2|.又x∈[
,1],故|x-2|=2-x,即x-2≤ax+1≤2-x.
∴1-
≤a≤
-1在[
,1]上恒成立.
(
-1)min=0,(1-
)max=-2,
∴-2≤a≤0.
故a的取值范围为[-2,0].
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824052525270338.png)
∴1-
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824052525363384.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824052525395314.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824052525270338.png)
(
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824052525395314.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824052525363384.png)
∴-2≤a≤0.
故a的取值范围为[-2,0].
![](http://thumb.zyjl.cn/images/loading.gif)
练习册系列答案
相关题目