The vertex form of a quadratic equation is y = n(x − h)2 + k, where (h, k) gives the coordinates of the vertex of the parabola in the xy-plane and the sign of the constant n determines whether the parabola opens upward or downward.
If n is negative, the parabola opens downward and the vertex is the maximum.
The given equation has the values h = 3, k = a, and n = −1.
Therefore, the vertex of the parabola is (3, a) and the parabola opens downward.
