题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012103-35286.png)
(1)修1m旧墙的费用是造1m新墙费用的25%;
(2)拆去1m旧墙用所得的材料来建1m新墙的费用是建1m新墙费用的50%.问如何利用旧墙才能使建墙的费用最低?
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012104-36400.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012104-75624.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012104-25163.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012104-47280.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012104-74889.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012105-43611.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012105-13997.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012105-89080.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012105-50994.png)
于是,所需的总费用为:
y=y
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012104-36400.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012104-74889.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012105-89080.png)
=[(
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012106-17541.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012106-87903.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012106-14244.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012106-70276.png)
当且仅当
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012107-39147.png)
故保留12 m的旧墙时总费用为最低。
解析
核心考点
试题【某学校校办工厂有毁坏的房屋一座,留有一面14m的旧墙,现准备利用这面墙的一段为面墙,建造平面图形为矩形且面积为126的厂房(不管墙高),工程的造价是:(1)修1】;主要考察你对均值不等式等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012058-87455.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012058-65768.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012058-89067.png)
A
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012058-67575.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012058-50689.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012059-59000.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012059-71682.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012047-68670.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012047-81526.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012048-53683.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012041-99043.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012041-90011.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012041-55629.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012042-48437.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012036-98141.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012036-52661.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012031-40972.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191016/20191016012031-14753.png)
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