If the take the origin as the starting point of the ball, then the vertex would be (4,28) and the parabola would be facing downwards. Using the general form of the parabola which is (x-h)^2 = 4p(y-k) where h and k are taken from the coordinate of the vertex (h,k).
So, the equation would be, (x-4)^2)=4p(y-28). To determine 4p, we can substitute either of the two points: (0,0) or (0,8). The second coordinate is taken from the given that the ball covers a distance of 4 ft after it reaches a maximum height. The total distance traveled by the ball is twice that, which is 8 ft.
After substituting, 4p = -4/7. Plugging this into the equation and after expanding and simplifying, the equation of the ball's trajectory is:
y = (-4/7)x^2+14x
