Gmat Maths Question Help?

Question

I need help with this Gmat problem. Kaplan has explained it in their website but I dont get their explanation. Any help would be appreciated.

If X and Y are positive and X>Y, is X-Y² ?

1. √X-Y = Y
2. X>1/2 Y

Answer 1

If X and Y are positive and X>Y, is X-Y²

1. √X-Y = Y
Let x = 10 and Y=1. Then √X-Y = Y fails to be true.

2. X>1/2 Y
If x > y, then x certainly >y/2.

I think I don't understand the question as stated. What does x-y^2 have to do with all of this?

is x-y^2 = to what?
Incidentally, I assume the √ applies only t x and not to x-y, else you would have parentheses around x-y.