Let

be the quadratic function that passes through the points (6,-3) and (3,0), then we get that:

Now, notice that a≠0 because y=a(x-h)² is a quadratic equation, therefore, from the last equation we get:

Adding h to the above equation we get:

Substituting h=3 in -3=a(6-h)² we get:

Simplifying the above equation we get:

Dividing the above equation by 9 we get:

Answer:
