x- coordinate of vertex = - 3
the vertex lies on the axis of symmetry , which is positioned at the midpoint of the zeros
find the zeros by setting y = 0
(x - 6)(x + 12) = 0 ( equate each factor to zero and solve for x )
x - 6 = 0 ⇒ x = 6
x + 12 = 0 ⇒ x = - 12
x coordinate of vertex = [tex]\frac{- 12+6}{2}[/tex] = [tex]\frac{-6}{2}[/tex] = - 3
