y(-1/2) = 0
y(2) = 0
c = -1
b = -3/2
C(0,-1)
所以P点y 坐标必须是-1/2
P((3+sqrt(17))/4,-1/2)
ACB = 90度
过A(-1/2,0)点与CB平行的直线交抛物线于Q(5/2,3/2)
y(-1/2) = 0
y(2) = 0
c = -1
b = -3/2
C(0,-1)
所以P点y 坐标必须是-1/2
P((3+sqrt(17))/4,-1/2)
ACB = 90度
过A(-1/2,0)点与CB平行的直线交抛物线于Q(5/2,3/2)