Thực hiện phép tính sau

Đáp án:

`a)` Đk: `x != -2`

`(x^3 - 1) / (x + 2) : (x^2 + x + 1)`

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

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

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

``

`b)` Đk: `x != +-sqrt(2), x != -1`

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

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

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

`= (x - 1) / (x + 1)`