-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