`color{#528B8B}{#A} color{#79CDCD}{n} color{#8DEEEE}{a} color{#97FFFF}{x} color{#BBFFFF}{a} color{#AFEEEE}{~}`

Đáp án `+` Giải thích các bước giải:

`a) (2 - 4x) (2 + 4x)`

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

`= 4 + 8x - 8x - 16x^2`

`= -16x^2 + (8x - 8x) + 4`

`= -16x^2 + 4`

`b) (4x + 1) . (4x + 1)`

`= 4x (4x + 1) + 1 (4x+ 1)`

`= 16x^2 + 4x + 4x + 1`

`= 16x^2 + 8x + 1`

`c) (x + 4) (x+4) (x + 4)`

`= (x^2 +8x+16)(x+4)`

`= x^2 (x+4) + 8x (x + 4) + 16(x+4)`

`= x^3 + 4x^2 + 8x^2 + 32x + 16x + 64`

`= x^3 + 12x^2 + 48x + 64`

`d) ( x- 2) (x-2) (x-2)`

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

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

`= x^3 - 2x^2 - 4x^2 + 8x + 4x - 8`

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

`e) (x+3 ) (x^2 - 3x + 9)`

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

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

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

`= x^3 + 27`

`g) (x^2 + x - 1) (x^2 + x - 1)`

`= x^2 (x^2 + x - 1) + x (x^2 + x - 1) - 1 (x^2 + x - 1)`

`= x^4 + x^3 - x^2 + x^3 + x^2 - x - x^2 - x + 1`

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

`= x^4 + 2x^3 -x^2 - 2x + 1`