When you need to compute the square root of a number you can do it by breaking it into perfect squares. When you can split the given number into small perfect squares you can cancel out the square root of the expression to the square of the perfect squares. You cannot always write the number inside the square root as a perfect square, but try to write this number as a product of a perfect square and another number. Now you can pull out the perfect square out of the radical and leave the remaining number inside the square root. This is the simplest form in which the rational expression can be represented.