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给出方程(a,b,c∈R)和三个结论:①方程的曲线是双曲线;②方程的曲线是椭圆或...
给出方程
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(a,b,c∈R)和三个结论:①方程的曲线是双曲线;②方程的曲线是椭圆或圆;③方程无轨迹.下面的说法一定正确的是( )
A.只有①正确
B.只有②正确
C.③不正确
D.①②③都有正确的可能
考点分析:
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曲线y=1+
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(-2≤x≤2)与直线y=k(x-2)+4有两个交点时,实数k的取值范围是( )
A.[
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,+∞)
B.(
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,
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]
C.(0,
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)
D.(
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,
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]
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设双曲线
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=1(0<a<b)的半焦距为c,直线l过(a,0)(0,b)两点,已知原点到直线l的距离为
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,则双曲线的离心率为( )
A.2
B.
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C.
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D.
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P(x,y)是椭圆
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+
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=1上的动点,过P作椭圆长轴的垂线PD,D是垂足,M是PD的中点,则M的轨迹方程是( )
A.
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+
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=1
B.
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+
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=1
C.
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+
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=1
D.
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+
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=1
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椭圆mx
2+y
2=1的离心率是
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101230919274359171/SYS201311012309192743591005_ST/0.png)
,则它的长半轴的长是( )
A.1
B.1或2
C.2
D.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101230919274359171/SYS201311012309192743591005_ST/1.png)
或1
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以椭圆短轴为直径的圆经过此椭圆的焦点,则椭圆的离心率是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101230919274359171/SYS201311012309192743591004_ST/0.png)
B.
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C.
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D.
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