题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-42547.jpg)
(1)设矩形的一边为
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-56835.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-56835.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
(2)当
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-56835.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-53072.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-48362.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-95444.png)
则
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-56835.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061805-73328.png)
=
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-53072.png)
自变量
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
(2)∵
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-56835.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-53072.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061805-38843.png)
∴ 当
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
最大面积是81
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061805-99078.png)
又解: ∵
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061805-70477.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061804-56835.png)
∴ 当
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061803-65739.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061805-13487.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061806-37166.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061805-99078.png)
(1)篱笆只有两边,且其和为18,设一边为x,则另一边为(18-x),根据公式表示面积;据实际意义,0<x<18;
(2)根据函数性质求最值,可用公式法或配方法.
核心考点
试题【如图,用长为18 m的篱笆(虚线部分),两面靠墙围成矩形的苗圃.(1)设矩形的一边为(m),面积为(m2),求关于的函数关系式,并写出自变量的取值范围;(2)当】;主要考察你对二次函数定义等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061759-87669.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061800-26920.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061800-64460.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061753-40617.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061753-47418.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061753-40617.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061753-69186.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061753-40617.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061754-76325.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061753-69186.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061754-71740.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061754-32362.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061754-36712.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061754-97320.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061755-57507.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061755-57047.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061755-57507.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061755-72386.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061737-92781.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061737-34076.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-50122.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-46022.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-96713.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-12720.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061739-49696.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061739-41507.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061739-28569.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-96713.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061739-96195.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061739-16984.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-33991.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-31358.png)
(1)求正方形
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061737-92781.png)
(2)当点
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-96713.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-46044.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-85569.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061741-43482.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-33991.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061739-16984.png)
(3)求(2)中面积
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061741-43482.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-33991.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061741-43482.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-96713.png)
(4)若点
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061739-16984.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-96713.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-46044.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061741-25468.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-33991.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061741-85190.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061741-25468.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061740-33991.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-96713.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061741-97533.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061738-96713.png)
(抛物线
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061742-52503.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061742-92442.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061727-82461.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061727-89622.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061727-40627.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061728-17636.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061728-11679.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061728-17636.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061728-82349.png)
(1)求点
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061728-17636.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061727-82461.png)
(2)求二次函数的解析式及它的最小值.
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061722-60391.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019061722-88314.jpg)
(1)求a的值.
(2)求点F的坐标.
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