Đáp án:+Giải thích các bước giải:

`a, (2 - 3x)^2 - 5x(x - 4) + 4(x - 1)`

`= 2^2 - 2.2.3x + (3x)^2 - (5x^2 - 20x) + (4x - 4)`

`= 4 - 12x + 9x^2 - 5x^2 + 20x + 4x - 4`

`= (9x^2 - 5x^2) + (-12x + 20x + 4x) + (4 - 4)`

`= 4x^2 + 12x`

`b, (3 - x)(x^2 + 3x + 9) + (x - 3)^3`

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

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

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

`= -9x^2 + 27x`

`c, (x - 4)^2 (x + 4) - (x - 4)(x + 4)^2 + 3(x^2 - 16)`

`= (x - 4)^2 (x + 4) - (x - 4)(x + 4)^2 + 3(x - 4)(x + 4)`

`= (x - 4)(x + 4)[(x - 4) - (x + 4) + 3]`

`= (x^2 - 16)(x - 4 - x - 4 + 3)`

`= (x^2 - 16).(-5)`

`= -5x^2 + 80`