I've corrected the TeX in my post now - the Android app is really nasty.
You've been given the next step by @Tbarker1. Note that (a+1+a)(a+1−a)=a+1−a=1
The denominator is of the form a+b, so if you multiply by a−ba−b (which is 1, when a and b aren't equal), it'll reduce the denominator to a2−b2, removing the surds.
I've corrected the TeX in my post now - the Android app is really nasty.
You've been given the next step by @Tbarker1. Note that (a+1+a)(a+1−a)=a+1−a=1
You might initially find it simpler to rewrite the equation using x=a+1 and y=a - it'd save writing square roots all over the place, until you get to the stage where you can simplify further. Otherwise, I prefer using a half power rather than a square root sign - IMO, it's less messy.