Đáp án:

`a) A = (x - 3)(x^2 + 3x + 9) - (x^3 + 3)`

`A = (x - 3)(x^2 + 3x + 3^2) - x^3 - 3``

`A = x^3 - 3^3 - x^3 - 3`

`A = (x^3 - x^3) + (-27 - 3)`

`A = -30`

`b) B = (2x + 1)(4x^2 - 2x + 1) - 8(x + 1/2)(x^2 - 1/2x + 1/4)`

`B = (2x + 1)[(2x)^2 - 2x + 1^2] - 8(x + 1/2)[x^2 - 1/2x + (1/2)^2]`

`B = (2x)^3 + 1^3 - 8[x^3 + (1/2)^3]`

`B = 8x^3 + 1 - 8(x^3 + 1/8)`

`B = 8x^3 + 1 - 8x^3 - 1`

`B = (8x^3 -8x^3) + (1 - 1)`

`B = 0`