Đáp án + Giải thích các bước giải:

`1) (x - 3)^3 - (x + 3)^3`

`= x^3 - 9x^2 + 27x - 27 - (x^3 + 9x^2 + 27x + 27)`

`= x^3 - 9x^2 + 27x - 27 - x^3 - 9x^2 - 27x - 27`

`= - 18x^2 - 54`

`2) (x + 2)^3 - (x + 6)(x^2 + 12) + 64`

`= x^3 + 6x^2 + 12x + 8 - (x^3 + 12x + 6x^2 + 72) + 64`

`= x^3 + 6x^2 + 12x + 8 - x^3 - 12x - 6x^2 - 72 + 64`

`= 0`

`3) (3 - x)^3 - x(2x + 1)^2 + 5(x - 3)(x + 3)`

`= 27 - 27x + 9x^2 - x^3 - x(4x^2 + 4x + 1) + 5(x^2 - 9)`

`= 27 - 27x + 9x^2 - x^3 - 4x^3 - 4x^2 - x + 5x^2 - 45`

`= -5x^3 + 10x^2 - 28x - 18`