Question 494165
It's a little easier to keep f(x) = x * (400-x) [just 1 multiply].
The plot is x axis and f(x) axis, just plug in the x values.
f(50) = 50 * 350 = 10500, so (50, 10500) is one point.
f(100) = 100 * 300 = 30000, so (100, 30000) is another point.
etc.
As a double check, x = 200 should be the largest f(x), 40000.