3)^3; B = (x - 1)(x^2 + x + 1) - (x - 2)(x^2 + 4x + 4); C = (3x - 1)^3 + (3x + 1)^3

Rút gọn:
A = (x - 1/3)^3 + (x + 1/3)^3
B = (x - 1)(x^2 + x + 1) - (x - 2)(x^2 + 4x + 4)
C = (3x - 1)^3 + (3x + 1)^3