where did the 9 come from?
Actually there's a quicker way. A (vertical) parabola has the form:
where the vertex is at (h, k) and it opens upward if a > 0 and opens downward if a < 0.
So the vertex of is at (-4, -7) and a = 1. Thus it opens upward. So it must be decreasing on and increasing on .
-Dan