def algo(x_A,y_A,x_B,y_B,x_C,y_C) :
	message = 'les 3 points ne sont pas pas alignés'
	if x_A == x_B and x_A == x_C:
		message = 'x =' + str(x_A)
	elif y_A == y_B and y_A == y_C:
		message = 'y =' + str(y_A)
	elif x_A != x_B and x_A != x_C:
		m1 = (y_B-y_A)/(x_B-x_A)
		m2 = (y_C-y_A)/(x_C-x_A)
		if (round(m1,10)) == (round(m2,10)):
			p = y_A-m1*x_A
			message = 'y =' + str(m1) + 'x + ' + str(p)
	return message