The vertex coordinates they provide are (-2, 5), and the point that the parabola passes through is (0, 9). First, I mentally imagined the points on a plane to determine whether "a" was positive or negative; then I took the coordinates from the vertex point, which represent (h, k), and sent up my problem. It came out to be y = (x + 1)^2 - 5, but in the answer key the 5 (which is k) was positive. Why is this so?