you can't do it individually because it is the same as:
to do this you have to subtract .can you do that?
As you were told above, the square root of a sum/difference is NOT equal to the sum/difference of the square roots. So you can't take each term in the numerator to the 1/2 power.
However, the square root of a product/quotient DOES equal the product/quotient of the square roots. So you CAN take the square root of the numerator and the square root of the denominator.