Y = 1/4x 2-x-8。
y(max)=(4ac-b^2)/4a=-9
According to the meaning of the question
Let BP pay AC to D.
Because S△BAD=S△BCD
So AD=CD
The d coordinate is (4, -4)
The vertex of the parabola is (m, -4).
The coordinates of point P are {(x, y)|x=2y-4} and y=-4}.
P(4,-4)
m=4