题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052220-48389.png)
(1)求该函数的关系式;
(2)若将该函数图象以顶点为中心旋转
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052221-19100.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052221-40228.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052221-41560.png)
解析
试题分析:(1)易知A点为二次函数的顶点,所以对称轴
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052221-26255.png)
根据顶点式可知
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052221-63104.png)
把A(-1,4)代入上式得:
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052222-38852.png)
代入B(2,0)后,求出a=
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052222-90739.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052221-40228.png)
(2)易知以A点为中心旋转后图像变为开口向上,a值改变为正数。则
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052221-41560.png)
点评:本题难度中等,主要考查学生对顶点式的掌握与运用。除了一般式之外,中考中也常会涉及顶点式求函数系数等,学生需要牢固掌握。
核心考点
试题【已知二次函数的图象以A(-1,4)为顶点,且过点B(2,0)(1)求该函数的关系式;(2)若将该函数图象以顶点为中心旋转,求旋转后抛物线的关系式.】;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/20191019/20191019052216-14407.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052216-95405.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052216-45066.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052216-83684.jpg)
A.有两个不相等的实数根 | B.有两个异号实数根 |
C.有两个相等实数根 | D.无实数根 |
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052212-18353.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052212-53035.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052212-33162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052212-56029.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052212-93244.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052213-49942.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052212-33162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052212-93244.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052213-49942.png)
A.![]() ![]() ![]() | B.![]() ![]() ![]() | C.![]() ![]() ![]() | D.![]() ![]() ![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052206-51104.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052206-25359.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052206-66610.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052206-46613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052156-64586.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052156-11689.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052157-61926.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052157-12824.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052157-98286.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052157-27116.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052158-20968.jpg)
A.2个 | B.3个 | C.4个 | D.5 |
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019052152-15097.png)
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