以(1,-1)为中点的抛物线y^2=8x的弦所在的直线方程为

要过程
2025-06-28 10:21:28
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回答1:

设所求直线为直线AB且A(x1,y1),B(x2,y2)C(1,-1)为线段AB的中点∴有(x1+x2)/2=1,(y1+y2)/2=-1即x1+x2=2,y1+y2=-2∴y1^2=8x1y2^2=8x2两式相减得(y1+y2)(y1-y2)=8(x1-x2)则(y1-y2)/(x1-x2)=8/(y1+y2)=-4即kAB=(y1-y2)/(x1-x2)=-4∴直线AB的方程为y+1=-4(x-1)即4x+y-3=0所以所求直线4x+y-3=0