X^2 -2XY +Y^2=36 so X-Y =?

My solution:(Not so sure...)

X^2 -2XY +Y^2=(X - Y)^2

Therefore, (X - Y)^2=36 So, X-y=6

But it is also a choice question and here are the choices:

6

+-6 (Postive or negative six) (could it be?)

-6

18.

Thank you in advance!

Guest Apr 30, 2019