Square root, also called quadratic root, is expressed as [√￣], where the square root of a non-negative number is called an arithmetic square root. A positive number has two real square roots, which are opposites of each other; 0 has only one square root, which is 0 itself; negative numbers have two conjugate pure imaginary square roots. Generally, "√￣" is only used to represent arithmetic square roots, that is, non-negative square roots. For example: √16=4.

If a positive number has a square root, then there must be two of them, and they are opposite numbers. Obviously, if we know one of the two square roots, then we can get the other square root in time based on the concept of opposite numbers.