y=a(x-h)^2+k is called vertex form of a quadratic function. When a quadratic function is written in vertex form, we can easily determine the vertex (h, k). If the coefficient a > 0, then the parabola opens upward and the vertex is the lowest point on the parabola. We say that k is the minimum value of the quadratic function. On the other hand, if the coefficient a < 0, then the parabola opens downward and the vertex is the highest point on the parabola. In this case, k is the maximum value of the quadratic function
y=-(x-10)^2+75
(h,k)=(10,75)
Maximum height of the diver above water is 75m.