`a)A = (1 + 1/sqrt(x))(1/(sqrt(x) + 1) + 1/(sqrt(x) - 1) - 2/(x - 1))`

(ĐKXĐ: `x > 0, x != 1`)

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

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

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

`= (sqrt(x) + 1)/sqrt(x) * 2 / (sqrt(x) + 1)`

`= 2/sqrt(x)`

Vậy `A = 2/sqrt(x)` với `x > 0, x != 1`