Hi Azza,
P(x) = -2x^2+4x+25
There are a couple of ways to determine the vertex, or maximum.
One way is to determine the coordinates of the vertex directly from this equation.
Vx = -b/2a = -4/[2(-2)] = 1
Then
Vy = P(1) = -2(1^2)+4(1)+25 = -2+4+25 = 27
The maximum is at (1,27)

Mark B.
12/22/16