If x = 2, y = 1 and z = -3, then x³ + y³ + z³ - 3xyz is equal to?

$$\eqalign{ & {\text{According to the question,}} \cr & x = 2,{\text{ }}y = 1,{\text{ }}z = - 3 \cr & {x^3} + {y^3} + {z^3} - 3xyz = ? \cr & {\text{As we know that}} \cr & a + b + c = 0{\text{ then }}{a^3} + {b^3} + {c^3} - 3abc = 0 \cr & 2 + 1 - 3 = 0 \cr & \therefore {x^3} + {y^3} + {z^3} - 3xyz = 0 \cr} $$