(2a + b)^2(b - 2a) = (4a^2 + 4ab + b^2)(b - 2a) = 4a^2b - 8a^3 + 4ab^2 - 8a^2b + 4ab^2 - 8b^3 = -8a^3 - 12a^2b + 8ab^2 - 8b^3
(3a - 4b)^2(3a + 4b) = (9a^2 - 24ab + 16b^2)(3a + 4b) = 27a^3 + 36a^2b - 72ab^2 + 36ab^2 - 48b^3 + 64b^3 = 27a^3 + 36a^2b - 36ab^2 + 16b^3
(2a + b)^2(b - 2a) = (4a^2 + 4ab + b^2)(b - 2a) = 4a^2b - 8a^3 + 4ab^2 - 8a^2b + 4ab^2 - 8b^3 = -8a^3 - 12a^2b + 8ab^2 - 8b^3
(3a - 4b)^2(3a + 4b) = (9a^2 - 24ab + 16b^2)(3a + 4b) = 27a^3 + 36a^2b - 72ab^2 + 36ab^2 - 48b^3 + 64b^3 = 27a^3 + 36a^2b - 36ab^2 + 16b^3