The equation of this parabola will have the form f(x) = a(x+5)(x-4), which works out to f(x) = a(x^2 + x - 20). Since the parabola passes thru (3,40),
40 = a(3^2 + 3 - 20), or 40 = a(-8), so a = -5.
Thus, the equation of this parabola is y = -5(x^2 + x - 20).
