
Bradford T. answered 10/14/20
Retired Engineer / Upper level math instructor
This function is a parabola opening downward. You can find where it crosses the x-axis by setting it equal to zero and solving for x.
-x^2/4 + 300 x = 0 --> (x-1200)x = 0
The x-axis crossings are at zero and x = 1200. The maximum x value is half way between these two points, or
x = 600. In other words, the axis of symmetry is -b/2a = -300/(2(-1/4)) = 600.