题目
题型:不详难度:来源:
且x1+x2=1-a, 则 ( )
A. y1< y2 | B. y1= y2 | C. y1> y2 | D. y1与y2的大小不能确定 |
答案
解析
解:将x1代入抛物线,得y1=ax12+2ax1+4,将x2代入抛物线,得y2=ax22+2ax2+4,
y1-y2=a(x12-x22)+2a(x1-x2)
=a(x1-x2)(x1+x2)+2a(x1-x2)
=a(x1-x2)(x1+x2+2)
∵x1+x2=1-a,
∴y1-y2=a(x1-x2)(3-a),
∵0<a<3,x1>x2,
∴y1-y2<0,即y1>y2.
故选C.
核心考点
试题【已知抛物线y=ax2+2ax+4(0<a<3),A(x1,y1)B(x2,y2)是抛物线上两点,若x1>x2,且x1+x2=1-a, 则 ( 】;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/20191019/20191019083538-42069.png)
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![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083538-42069.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083538-42069.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083538-42069.png)
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![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083538-42069.png)
则a的值为___________.
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083538-52285.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083523-15562.png)
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![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083524-86781.png)
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![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083523-47631.png)
小题1:求a、b、c的值;
小题2:若点
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083524-30656.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083524-99021.png)
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![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083525-81849.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083525-10290.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083524-99021.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083525-17026.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083526-78708.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083526-78708.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083526-81499.png)
小题3:上下平移该抛物线得到新的抛物线,设新抛物线的顶点为D,对称轴与x轴的交点为E,若△ODE与△OBC相似,求新抛物线的解析式。
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083526-74601.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083516-71695.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083516-81068.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083516-45595.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083517-50487.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083517-22767.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083517-16538.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083517-97957.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191019/20191019083511-30562.png)
A.(1,0) | B.(-1,0) | C.(1,-1) | D.(1,1) |
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