(1/3 ab^2 + b^2)^3 = (1/3)^3 (ab^2)^3 + 3 ((1/3)^2 (ab^2)^2 b^2) + 3 ((1/3) b^2 b^2) + b^6= 1/27 a^3 b^6 + 1/3 a^2 * b^4 + b^4 + b^6
(1/3 ab^2 + b^2)^3 = (1/3)^3 (ab^2)^3 + 3 ((1/3)^2 (ab^2)^2 b^2) + 3 ((1/3) b^2 b^2) + b^6
= 1/27 a^3 b^6 + 1/3 a^2 * b^4 + b^4 + b^6