1) the form of the equation may be written as y = A(X - Xo)(X - X1)
Where Xo and X1 are the two roots of the equation.
2) We can fix the system of coordinates so that the vertex is in the middle of the gate => Xo = - 40 and X1 = +40
=> y = A (X + 40) (X - 40) = A (X^2 - 1600)
3) The height, at X = 0 is 25
=> A(0 - 1600) = 25
=> -1600A = 25 => A = -25 / 1600 = - 1/64
4) The equation is y = - [1/64] (X^2 - 1600)
5) You can present it in different equivalent forms.
Some of those other forms are:
1) - 64y = (x^2 - 1600)
2) x^2 = - 64y + 1600
3) X^2 = - 64 (y - 25)
