12a平方b(x-y)三次方-4ab(y-x)平方 12a^2 b (x-y)^3 - 4ab(y-x)^2 = 4ab(x-y)^2 * [ 3a(x-y) - 1] （a平方-4a）平方+（3a-12)平方 (a^2 - 4a)^2 + (3a-12)^2 = a^2(a-4)^2 + 9(a-4)^2 = (a-4)^2 * (a^2 - 9) = (a-4)...