c) x^3 + 9x^2y + 27xy^2 + 27y^3;
c) x3 + 9x2y + 27xy2 + 27y3;
c) x3 + 9x2y + 27xy2 + 27y3
= x3 + 3 . x2. 3y + 3 . x . (3y)2 + (3y)3 = (x + 3y)3;