-6 6 setxrange
-4 4 setyrange
quadrillage

/f {
   3 div 2 3 div sub
}  def

tracerepere
marks
-1 dup f dashpoint
2 dup f point

1.2 setlinewidth
{f} courbe

setTimesItalic
   (O) 0 0 dltext

<tex>
$y = ax+b$
</tex>

-4 dup f [1.2 dup] {-2 dup f 0 dup f angle} uctexlabel