-3 1 setxrange
-2 2 setyrange
20 setxunit

traceOx

xticks
0 xtick
[-2 -1 0] {xmark} apply

/A {xmin 0} def
/B {-1.67 0} def
/C {-1.67 -0.5} def
1.7 setlinewidth

<tex>
$$
   5 \over -3
$$
</tex>

C drtexlabel

[A B] (-[) ligne