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已知双曲线3x2-y2=3,过点P(2,1)作直线l交双曲线于A,B两点.
(1)求弦AB中点M的轨迹.
(2)若P恰为AB中点,求l的方程.
人气:213 ℃ 时间:2019-11-15 07:37:00
解答
(1)设A(x1,y1),B(x2,y2),M(x,y),
则3x12-y12=3,3x22-y22=3,
两式相减得3x(x1-x2)-y(y1-y2)=0,
3x
y
y−1
x−2
,即3x2-y2-6x+y=0,斜率不存在时也满足,轨迹为双曲线;
(2)由(1)知3x12-y12=3,3x22-y22=3,
两式相减得6(x1-x2)-(y1-y2)=0,从而直线的斜率为6,
故所求直线方程为6x-y-11=0
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