-2 3 setxrange -1 9 setyrange 2 setxyrapport /f { dup % x, x 3 mul % x, 3x 2 sub % x, 3x-2 mul % 3x^2-2x 1 add } def tracerepere marks 0 dup f point -1 dup f dashpoint 1 dup f dashpoint 1.2 setlinewidth {f} courbe setTimesItalic (O) 0 0 dltext