`sqrt(18 + 2sqrt(17))`

`= sqrt(17 + 2sqrt(17) + 1)`

`= sqrt((sqrt(17) + 1)^2)`

`=|sqrt(17)+1|`

`= sqrt(17) + 1`

`---------`

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

`= 3|x| - x + 1`

TH1: `x >= 0 `

`3x - x + 1 = 2x + 1`

TH2: `x < 0` 

`3(-x) - x + 1 = -4x + 1`

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