To simplify #sqrt48#, we should first factorize #48#. As #2# is one factor, dividing 48 by 2, we get 24, which has factors 2 again. This way we go on till we get all the factors.
Hence #sqrt48=sqrt(2xx2xx2xx2xx3)#.
As #2# has appeared four times, square root of #2xx2xx2xx2# will be just #2xx2#. Note we cannot take square root of #3# as it has not appeared in pair.
Hence, #sqrt48=2xx2xxsqrt3# or #4sqrt3#