Explanation:
so when you want to rationalize the denominator when it's in the form
you multiply by the conjugate which is
which is where the sign is the opposite. This is because it's using the difference of squares to get rid of the square root. Because
this will remove the square root since it's going to become square and the ab - ab will cancel so there will be no square root
Multiply by conjugate

Simplify:

Simplify radical

You could go further and do
