y^2=2x x=y^2/2
A(y1^2/2,y1) B(y1^2/2,y1)
(1)
OA斜率k1=y1/(y1^2/2)=2/y1
OB斜率k2=y2/(y2^2/2)=2/y2
k1*k2=-1
(2/y1)(2/y2)=-1
y1*y2=-4
x1*x2=(y1^2/2)(y2^2/2)=(y1*y2)^2)/4=4
(2)
AB中点M(x,y)
y=(y1+y2)/2
△ABO为直角三角形
M为斜边AB的中点
MO=AB/2
x^2+y^2=((y1^2/2-y2^2/2)^2+(y1-y2)^2)/2
解
y=(y1+y2)/2
x^2+y^2=((y1^2/2-y2^2/2)^2+(y1-y2)^2)/2
y1*y2=-4
得
y^2=x-2