gmat prep question

[vaivish]

need help on this on,....

[4meonly]

because under square root you can have only positive number and is x<0,
-x*mod(x) wiil yield a posive number, here -x

try it with -5, you'll get 5

[stop@800]

4meonly has given good solution.

An alternate would be take x = -y
and solve for y
and at end replace with x

HTH