Source
25 setxunit
7.5 setborder
90 setangle_repere
-5 5 setxrange
-5 5 setyrange
1 1 settkstep
.5 .5 setsubtkstep
1 1 setmkstep
ticks
marks
traceaxes
axesarrow
/f {setxvar
#rpn#   1/x
} def
/g {setxvar
#rpn#   4/x
} def
/h {setxvar
#rpn#   9/x
} def
gsave
   noir
   .75 setlinewidth
   continu
   {f} courbe
   {h} courbe
   {g} courbe
grestore