1.(p/2,0)
y1^2=2px1
y2^2=2px2
y1^2y2^2=4p^2x1x2
y1y2=-2p(x1x2)^1/2
y1y2/x1x2=-2p/(x1x2)^1/2
y=k(x-p/2)
y^2=2px
k^2(x-p/2)^2=2px
k^2x^2-pk^2x+1/4p^2k^2-2px=0
k^2x^2-(pk^2+2p)x+1/4p^2k^2=0
x1x2=1/4p^2
y1y2/x1x2=2p/1/2p=4
A
2.x^2=4y=2py
p=2
y=-1
x=0
(x0,y0)
y0=x0^2/4
/x0/=/y0+1/
x0^2=(y0+1)^2=4y0^2
y0^2+2y0+1=4y0^2
3y0^2-2y0-1=0
(3y0+1)(y0-1)=0
y0=-1/3(she)y0=1
x0=+-/3,x0=+-2
(+-2,1)
r=2
(x+-2)^2+(y-1)^2=4
x^2+y^2+-4x-2y+1=0
B
3.4-4x+x^2=k^2x^2
(k^2-1)x^2+4x-4=0
16+16(k^2-1)=16k^2>0
2