Radicals can be simplified through adding and subtracting, but you should keep in mind that you sometimes can't "cleanly" simplify square roots down into a number. The first thing to note is that radicals can only be added and subtracted if they have the same root number.
Can you add together radicals?
You can only add or subtract radicals together if they are like radicals. You add or subtract them in the same fashion that you do like terms shown in Tutorial 25: Polynomials and Polynomial Functions. Combine the numbers that are in front of the like radicals and write that number in front of the like radical part.
What are the rules for adding radicals?
To add radicals, the radicand (the number that is under the radical) must be the same for each radical. Subtraction follows the same rules as addition: the radicand must be the same. Multiplication of radicals simply requires that we multiply the term under the radical signs.