Rút gọn: a) (x - 3)(x + 3) - (x + 5)(x - 1); b) (3x - 2)^2(x + 1)^2 + c2(3x - 2(x + 1); c) (x + 2)(x^2 - 2x + 4) - (18x)^3; d) (2x - y)(4x^2 + 2xy + y)^2 - (2x + y)(4x^2 - y^2)