$a)-2x(-2x+2)-(x+2)^2$

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

$=4x^2-4x-x^2-4x-4$

$=3x^2-8x-4$

$b)(x+2)(x^2-2x+4)-2(x+1)(1-x)$

$=x^3-8-2(1+x)(1-x)$

$=x^3-8-2(1-x^2)$

$=x^3-8-2+2x^2$

$=x^3-10+2x^2$

$c)(2x-1)^2-2(4x^2-1)+(2x+1)^2$

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

$=[(2x-1)-(2x+1)]^2$

$=(2x-1-2x-1)^2$

$=(-2)^2$

$=4$

$#thanhmaii2008$

Đáp án:

`a) 3x^2 - 8x - 4`

`b) x^3 + 2x^2 + 6`

`c) 4`

Giải thích các bước giải:

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

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

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

`= 4x^2 - 4x - x^2 - 4x - 4`

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

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

`b)`

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

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

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

`= (x^3 + 8) + 2(x^2 -1)`

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

`= x^3 + 2x^2 + (8 - 2)`

`= x^3 + 2x^2 + 6`

`c)`

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

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

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

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

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

`= ( - 2)^2`

`= 4`

`#SunHee`