弦AB的中点M(-2,-3)
yA+yB=2yM=2*(-3)=-6
y^2=-12x
(yA)^2=-12xA.(1)
(yB)^2=-12xB.(2)
(1)-(2):
(yA+yB)*(yA-yB)=-12(xA-xB)
k(AB)=(yA-yB)/(xA-xB)=-12/(yA+yB)=-12/(-6)=2
y+3=2(x+2)
弦所在直线的方程:y=2x+1
弦AB的中点M(-2,-3)
yA+yB=2yM=2*(-3)=-6
y^2=-12x
(yA)^2=-12xA.(1)
(yB)^2=-12xB.(2)
(1)-(2):
(yA+yB)*(yA-yB)=-12(xA-xB)
k(AB)=(yA-yB)/(xA-xB)=-12/(yA+yB)=-12/(-6)=2
y+3=2(x+2)
弦所在直线的方程:y=2x+1