题目内容
(本小题满分12)
为了绿化城市,准备在如图所示的区域
内修建一个矩形
的草坪,并建立如图平面直角坐标系,且
,
,另外
的内部有一文物保护区不能占用,经测量
,
,
,
.
(1)求直线
的方程;
(2)应如何设计才能使草坪的占地面积最大?并求最大面积。![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240009179303248.png)
为了绿化城市,准备在如图所示的区域
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917774583.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917789538.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917805600.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917820577.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917836543.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917852607.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917867634.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917883640.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917898630.png)
(1)求直线
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917914386.png)
(2)应如何设计才能使草坪的占地面积最大?并求最大面积。
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240009179303248.png)
(1)
(2)
时,
最大,其最大值为![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917976788.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917945724.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917945726.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917961325.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917976788.png)
试题分析:(1)如图,在线段
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917992390.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000918008341.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000918023531.png)
由题意,直线
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917992390.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240009180541165.png)
(2)设
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000918070844.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240009180861466.png)
化简后得
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240009181012172.png)
易得
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000918117730.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917961325.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824000917976788.png)
点评:解决实际问题,关键是从实际问题中抽象出数学模型,再用数学知识解决,另外求解实际问题时,不要忘记实际问题满足的定义域.
![](http://thumb.zyjl.cn/images/loading.gif)
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