Question 1073021
.
{{{4x - x^2}}} = {{{-(x^2-4x)}}} = {{{-(x^2 - 4x + 4) + 4}}} = {{{-(x-2)^2+4}}}.


The vertex is (x,y) = (2,4).



{{{graph( 330, 330, -5.5, 6.5, -8.5, 6.5,
          -x^2 + 4x
)}}}


Plot y = {{{-x^2 + 4x}}}