In this case, we multiply the fraction by the square root of two, DIVIDED by the square root of two. Obviously, that is equal to one. Then, you just simplify.
On the denominator, you have the root of 2 multiplied by the root of 2, which is 2. On the top you get the square root of two, which is simply
Let me know if this makes sense.
EDIT: Also, obviously, I assume you know that the square root of 1 is 1.
(sorry) Yes, arcketer, you found one solution but not the other :
This is equivalent (obviously) to :
Therefore, taking the square root yields :
and (the square of a number is equal to the square of its opposite!)
Using properties of square roots, the solutions become :