from matplotlib import pyplot

def TRACER_SEGMENT(x1, y1, x2, y2) :
	pyplot.plot([x1,x2], [y1,y2]) 
def F1(x) :
	return x**3 - x**2

xdepart=-2
while (xdepart<4) :
	xfin=xdepart+pas
	TRACER_SEGMENT(xdepart,F1(xdepart),xfin,F1(xfin))
	xdepart=xfin
pyplot.show()