y^2=2px
A(2pa^2,2pa),B(2pb^2,2pb)
k(OA)*k(OB)=-1
[(2pa)/(2pa^2)]*[(2pb)/(2pb^2)]=-1
a=-1/b
k(AB)=(2pa-2pb)/(2pa^2-2pb^2)=1/(a+b)
AB:y-2pa=(x-2pa^2)/(a+b)
(a+b)y-2pb=x
(b-1/b)y-2pab=x
b=1,a=-1,x=y=2p
直线AB恒过定点A(2p,-2p),B(2p,2p)
y^2=2px
A(2pa^2,2pa),B(2pb^2,2pb)
k(OA)*k(OB)=-1
[(2pa)/(2pa^2)]*[(2pb)/(2pb^2)]=-1
a=-1/b
k(AB)=(2pa-2pb)/(2pa^2-2pb^2)=1/(a+b)
AB:y-2pa=(x-2pa^2)/(a+b)
(a+b)y-2pb=x
(b-1/b)y-2pab=x
b=1,a=-1,x=y=2p
直线AB恒过定点A(2p,-2p),B(2p,2p)