-5 3 setxrange -4 7 setyrange 25 setxunit /f { dup % x, x 4 add % x, x+4 mul % x^2+4x 1 add } def tracerepere marks [0 -1 1] {dup f} apply dashpoints 1.2 setlinewidth {f} courbe setTimesItalic (O) O drtext