A ball is thrown across a field. Its path is given by the equation
y = -0.005x^2 + x + 5
where:
y = height
x = horizontal distance
What is the max height reached by the ball?
If you're familiar with calculus, find where $\displaystyle \frac{\,dy}{\,dx}=0$ and then plug that value into the original function to find the maximum height.
Otherwise, you can use the fact that the vertex of a parabola occurs at the point $\displaystyle \left(-\frac{b}{2a},f\left(-\frac{b}{2a}\right)\right)$