题目内容
如图,直角梯形ABCD中,
A=90°,
B=45°,底边AB=5,高AD=3,点E由B沿折线BCD向点D移动,EM
AB于M,EN
AD于N,设BM=
,矩形AMEN的面积为
,那么
与
的函数关系的图像大致是( )
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240516512642221.jpg)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240516512806593.jpg)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824051651155258.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824051651155258.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824051651171183.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824051651171183.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824051651202275.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824051651218309.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824051651218309.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824051651202275.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240516512642221.jpg)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240516512806593.jpg)
A
试题分析:根据已知可得:点E在未到达C之前,y=x(5-x)=5x-x2;且x≤3,当x从0变化到2.5时,y逐渐变大,
当x=2.5时,y有最大值,当x从2.5变化到3时,y逐渐变小,
到达C之后,y=3(5-x)=15-3x,x>3,
根据二次函数和一次函数的性质.故选:A.
![](http://thumb.zyjl.cn/images/loading.gif)
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