过抛物线Y2=4X的焦点F的直线交抛物线于A,B两点,则1/AF+1/BF=?
过抛物线Y2=4X的焦点F的直线交抛物线于A,B两点,则1/AF+1/BF=?
数学人气：983 ℃时间：2019-08-20 23:49:12
优质解答
易知F坐标（1,0）准线方程为x=-1.设过F点直线方程为y=k(x-1)代入抛物线方程,得 k^2(x-1)^2=4x.化简后为：k^2*x^2-(2k^2+4)x+k^2=0.此方程的两个解为x1,x2.x1=[2k^2+4+4√(k^2+1)]/(2k^2)x2=[2k^2+4-4√(k^2+1)]/(2k^...
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