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 {4 5} def $P_i$ P [1.5 1.5] uctexlabel /M {3 5} def M dashpoint $M_i$ M [1.5 1.5] uctexlabel bleu /K {4 5} def $D:x=a'y+b'$ K [1.5 1.5] drtexlabel noir /Z {0 5} def $y_i$ Z [1.5 1.5] cltexlabel /W {3 0} def $x_i$ 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 {0.5 1.5} def /Y {1 1.5} def Y point [S Y] (-) ligne /S {6.8 7.8} def /Y {6 7.8} def Y point [S Y] (-) ligne /S {5 6} def /Y {5.5 6} def Y point [S Y] (-) ligne /S {6 7} def /Y {4.5 7} def Y point [S Y] (-) ligne /S {0.7 1.7} def /Y {2.5 1.7} def Y point [S Y] (-) ligne 1 setlinewidth noir /T {4 0} def pointilles [T P] ligne $a'y_i+b'$ T [1.5 1.5] drtexlabel