From the graph the vertex of the parabola is at ,

The parabola of the vertex is , , and .

The point on the graph of the parabola , and .

(Apply vertex form of the parabola equation: )

Now we can find a value.

(Substitute for h, for k, for x  and for y)

(Add 3 to each side)

(Divide each side by 4)

(Substitute for a, for h, and for k)

The vertex form of the parabola equation is .