def F1(x) :
	return x**3 - x**2

from matplotlib import pyplot
pas=0.1
xdepart=-2
X = []  # liste des abscisses
Y = []  # liste des ordonnees
while (xdepart<=4) :
	X.append(xdepart)
	Y.append(F1(xdepart))
	xdepart=xdepart+pas
pyplot.plot(X, Y)
pyplot.show()