Step-by-step explanation: set both (x +2) and (x-6) = 0.
You get the two x-intercepts -2 and 6. Find the midpoint of the two intercepts by -2 + 6 / 2 which gives you x=2. Then plug 2 in for x and solve the original equation. ( 2 - 6)(2+2) = -16. Therefore the vertex is at (2,-16).