Đáp án+Giải thích các bước giải:

`2)`

`[x-3]^2 - x^2 + 10x - 7 `

`= (x^2 - 6x + 9) - x^2 + 10x - 7 `

`= x^2 - x^2 - 6x + 10x + 9 - 7 `

`= 4x + 2`

`3)`

[x + 2]^2 - [x - 3][x + 1]`

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

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

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

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

`= 6x + 7 `

`4)`

`[x + 4][x - 2] - [x - 3]^2 `

`= (x^2 - 2x + 4x - 8) - (x^2 - 6x + 9) `

`= (x^2 + 2x - 8) - (x^2 - 6x + 9) `

`= x^2 + 2x - 8 - x^2 + 6x - 9 `

`= x^2 - x^2 + 2x + 6x - 8 - 9 `

`= 8x - 17 `

`5)`

`[x - 2]^2 + [x - 1][x + 5] `

`= (x^2 - 4x + 4) + (x^2 + 5x - x - 5) `

`= x^2 - 4x + 4 + x^2 + 4x - 5 `

`= x^2 + x^2 - 4x + 4x + 4 - 5 `

`= 2x^2 - 1`

`6)`

`[x + 3][x - 3] - x[23 + x] `

`= (x^2 - 3^2) - (23x + x^2) `

`= (x^2 - 9) - 23x - x^2 `

`= x^2 - x^2 - 9 - 23x `

`= -23x - 9`

`7)`

`[1 - 2x][5 - 3x] + [4 - x]^2`

`= (15 + 1(-3x) - 2x5 - 2x(-3x)) + (4^2 - 24x + x^2)`

`= (5 - 3x - 10x + 6x^2) + (16 - 8x + x^2) `

`= (6x^2 - 13x + 5) + (x^2 - 8x + 16) `

`= 6x^2 + x^2 - 13x - 8x + 5 + 16 `

`= 7x^2 - 21x + 21 `

`8)`

`[x - 2][x + 2] - [x - 3] + 10 `

`= (x^2 - 2^2) - (x - 3) + 10`

`= (x^2 - 4) - x + 3 + 10 `

`= x^2 - 4 - x + 3 + 10 `

`= x^2 - x + (-4 + 3 + 10) `

`= x^2 - x + 9 `