`ĐKXĐ: x >= 1` và `x != 2`

`B = 1 / sqrt((x - 1) + 2.sqrt(x - 1) + 1) + 1 / sqrt((x - 1) - 2.sqrt(x - 1) + 1)`

`B = 1 / sqrt((sqrt(x - 1) + 1)^2) + 1 / sqrt((sqrt(x - 1) - 1)^2)`

`B = 1 / (sqrt(x - 1) + 1) + 1 / |sqrt(x - 1) - 1|`

`TH1: 1 <= x < 2:`

Do `sqrt(x - 1) < 1` nên `|sqrt(x - 1) - 1| = 1 - sqrt(x - 1)`

Ta có:

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

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

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

`B = 2 / (2 - x)`

`TH2: x > 2:`

Do `sqrt(x - 1) > 1` nên `|sqrt(x - 1) - 1| = sqrt(x - 1) - 1`

Ta có:

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

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

`B = 2.sqrt(x - 1) / ((x - 1) - 1) `

`B = [2.sqrt(x - 1) ]/ (x - 2)`