1) (3а+b)^3 - (a+3b)^3 - 18ab(a-b) - 26(a^3 - b^3) = 3a^3 + b^3 -a^3 + 3b^3 - 18a^2 b + 18ab^2 - 26a^3 + 26b^3= -24a^3 +30b^3
2) (x+4y)^3 + (4x-y)^3 + 12xy(3x-5y)-128y^3- 65(x^3 - y^3) = x^3 + 4y^3 + 4x^3 - y^3 + 36x^2y - 69xy^2 - 128y^3 - 65x^3+ 65y^3 = -60x^3 - 60y^3 +36x^2y - 69xy^2