data sufficiency question

[syedrazi4u]

a=x+y and b=x-y if a^2=b^2,what is the value of y
1) sqrt x+sqrty>0
2) sqrt x-sqrt y>0

Answer is b according to advance gmat quant,but my question is in the solution why negative roots have not been consider ed A s Xy=0, in 2nd choice if x=0 and negative root is considered for y then also inequality would hold then. the answer should be E. Plz explain

[tim]

the easiest way to think of it is this: when you introduce the square root symbol as part of your work on a problem, you must account for positive and negative solutions. when the GMAT gives you a square root symbol as part of the problem, you are ALWAYS supposed to take only the positive square root..

[syedrazi4u]

Thanks for the guidance.Really appreciate

[jnelson0612]

Let us know if we can do anything else to help. :-)