-3.1 1.1 setxrange
-3 1 setxrange
-1 4.5 setyrange

.5 .5 setquadrillagestep
quadrillage
traceaxes
axesarrow

1 xmark
-3 xmark
1 ymark

/g {setxvar
#rpn# .5*x^2 + x
} def

.8 setlinewidth
{g} courbe

setTimesItalic
   (O) O drtext
   (x) xmax 0 ultext
   (y) 0 ymax dltext
   (P) xmax dup g bltext