We can start by figuring out the axis of symmetry.
y = x² + 12x = x (x + 12)
So roots are x = -12 or 0
Therefore axis of symmetry is x = (-12 + 0) / 2 = -6
We got x-coordinate of vertex. Now plug in x=-6 to solve for y.
y = (-6)² + 12(-6) = 36 - 72 = -36
Therefore vertex is (-6, -36).
