y = - 3(x + 1 )² + 2
the equation of a quadratic in vertex form is
y = a(x - h)² + k
where (h, k) are the coordinates of the vertex and a is a multiplier
here vertex = (- 1, 2), hence
y = a(x + 1)² + 2
to find a substitute (1, - 10) into the equation
- 10 = 4a + 2 ⇒ 4a = - 12 ⇒ a = - 3
y = - 3(x + 1)² + 2 ← in vertex form
