若抛物线y²=2px(p＞0)的弦PQ的中点为M(x0,y0)(y0≠0),则直线PQ的斜率为

若抛物线y²=2px(p＞0)的弦PQ的中点为M(x0,y0)(y0≠0),则直线PQ的斜率为

(yP)^2-(yQ)^2=2pxP-2pxQ
(yP+yQ)*(yP-yQ)=2p(xP-xQ)
2y0*(yP-yQ)/(xP-xQ)=2p
k(PQ)=(yP-yQ)/(xP-xQ)=p/y0