a/ -8x2 - 12xy3 - 4xy2 = -4x (2x + 3y3 + y2)
b/ (x - y)3 - x3 + y3 = x3 - 3x2y + 3xy2 - y3 - x3 + y3 = -3x2y + 3xy2 = -3xy (x - y)
c/ 3x(x - y) - 2y(x - y) = (x - y) (3x - 2y)
d/ a(x + 2) - 2b(x + 2) + (x + 2) = (x + 2) (a - 2b +1)
e/ 5x(x - y) - (y - x) = 5x(x - y) + (x - y) = (x - y) (5x + 1)