Equation of a parabola:
(y-k) = a(x-h)², where h & k are the pair of the vertex : vertex(h , k).In the example vertex(0.3), hence
y-3 = a(x-0)² →→ y = ax² + 3. Let's calculate the coefficient "a". To that end replace x & y by the given pair: (-4 , -45):
-45 = a(-4)² +3 → -45 = 16a +3 & a = -3
Finally the equation is y=-3x³ + 3