Explanation:
for that we best use the intercept form of a parabola equation :
y = a(x - p)(x - q)
p and q are the zeroes (x-intercepts) of the parabola.
a is the stretching factor (how wide or how narrow is the curve, and a positive "a" says it is opening upwards, a negative "a" says it is opening downwards).
so, our equation looks like
y = a(x - -2)(x - 5) = a(x + 2)(x - 5)
to get a we use the coordinates of the given point :
-40 = a(3 + 2)(3 - 5) = a×5×-2 = -10a
a = -40/-10 = 4
the equation is then
y = 4(x + 2)(x - 5) = 4(x² -5x + 2x - 10) =
= 4(x² - 3x - 10) = 4x² -12x - 40