解 y^2=2Px (1 )
y=3x-6 (2)
(3x-6)^2=2Px
9x^2-(36+2P)x+36=0
两解析式有交点 即△=0
(36+2P)^2-4*9*36=0
P1=-36 P2=0(不合题意舍去)
抛物线方程:y^2=-72X