How do you graph the function ##y=5x-x^2##?

graph{5x-x^2 [-14.24, 14.23, -7.12, 7.12]}

First you realise that ##5x-x^2=x(5-x)## which will give the ##y=0## solutions ##x=0## and ##x=5## for ##(0,0)## and ##(5,0)##

Then, put the halfway-##x## (##2.5##) in the equation to get the top of the graph ##y=5*2.5-2.5^2=6.25## for ##(2.5,6.25)##

You now have the three most important points of your graph. You can put more ##x##-values in, of course, so you get more points, but these three are essential.