25 setxunit
7.5 setborder
90 setangle_repere
-2 8 setxrange
-1 8 setyrange
1 1 settkstep
.5 .5 setsubtkstep
2 2 setmkstep
traceaxes
axesarrow
/f {setxvar
#rpn#   x+1
} def
gsave
   bleu
   .75 setlinewidth
   continu
   {f} courbe
grestore

/P {3 4} def


<tex>
$P_i$
</tex>
 P [1.5 1.5] drtexlabel

/M {3 5} def
M dashpoint

<tex>
$M_i$
</tex>
M [1.5 1.5] uctexlabel

bleu
/K {4 5} def
<tex> 
$D:y=ax+b$
</tex> 
K [1.5 1.5] drtexlabel

noir
/L {0 4} def

<tex> 
$ax_i+b$
</tex> 
L [1.5 1.5] cltexlabel

/Z {0 5} def

<tex> 
$y_i$
</tex> 
Z [1.5 1.5] cltexlabel

/W {3 0} def

<tex> 
$x_i$
</tex> 
W [1.5 1.5] dctexlabel

(0) 0 0 [1.5 1.5] dltext

1.5 setlinewidth

rouge

M point
P point
[P M] (-) ligne

/S {1 2} def
/Y {1 1.5} def
Y point
[S Y] (-) ligne

/S {6 7} def
/Y {6 7.8} def
Y point
[S Y] (-) ligne

/S {6 7} def
/Y {6 7.8} def
Y point
[S Y] (-) ligne

/S {5.5 6.5} def
/Y {5.5 6} def
Y point
[S Y] (-) ligne

/S {4.5 5.5} def
/Y {4.5 7} def
Y point
[S Y] (-) ligne

/S {2.5 3.5} def
/Y {2.5 1.7} def
Y point
[S Y] (-) ligne



1 setlinewidth

noir
/T {0 4} def
pointilles
[T P] ligne