Answer
The vertex: $(80,1600)$
Work Step by Step
Given
\begin{equation}
\begin{aligned}
y & =-0.25 x^2+40 x \\
a&= -0.25;\quad b= 40, \quad c= 0
\end{aligned}
\end{equation}
The $x$ and $y$ values of the vertex are given by:
\begin{equation}
\begin{aligned}
x &= -\frac{b}{2a}\\
& = -\frac{40}{2(-0.25)}\\
&= 80\\
y& =-0.25\cdot (80)^2+40\cdot (80) \\
& = 1600\\
\end{aligned}
\end{equation}
The vertex of the parabola is given by:$(80,1600)$
