-2.5 3.7 setxrange
-3 3 setyrange

1.9 setxyrapport
60 setxunit
7.5 setborder
90 setangle_repere
-2 3.6 setxrange
-3 3 setyrange

traceaxes
axesarrow

%unites
/f {setxvar
#rpn#   (-x^2+x+2)
} def

/g {setxvar
#rpn#   0
} def

4.2 setlinewidth
[-2.5 0 -1 0] ligne
[2 0 3.45 0] ligne


gsave
   noir
   0.5 setlinewidth
   continu
-2.5  3.5 {f} Courbe
grestore

noir
/hwidth .2 def
/hstep 8 def
2 3.5 {g} {f} Hachcourbes

noir
/hwidth .2 def
/hstep 8 def
-3 -1 {f} {g} Hachcourbes


<latex>
$a<0$
</latex>
1.2 -1.2 [1.8 dup] dltexlabel

<latex>
$x_1$
</latex>
-1 0 [1.8 dup] ultexlabel

<latex>
$x_2$
</latex>
2 0 [1.8 dup] urtexlabel