What are the rules for subtracting and adding radicals?

When adding or subtracting radicals, you can only combine them if they have the same index and the same radicand (the number inside the radical). For example, √2 + √2 equals 2√2, but √2 + √3 cannot be combined and remains as is. If the radicals are not like terms, you simply write them next to each other. Additionally, you can simplify radicals before performing the addition or subtraction if possible.