## Square Root

A square root of a number is another number that, when it is multiplied by itself (squared), gives the first number again. For example, 2 is the square root of 4, because 2×2=4. Only numbers bigger than or equal to zero have real square roots. The only square root of zero is zero.

Square roots of negative numbers are not real numbers – they are imaginary numbers. Imaginary numbers are basically numbers that cannot be square rooted and get a real result. Every complex number except 0 has 2 square roots. For example: −1 has two square roots. We call it i and -i.

A whole number with a square root that is also a whole number is called a perfect square. The first few perfect squares are: 0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 256, 289, 324, 361, 400, 441, 484, 529, 576, 625, 676, 729, 784, 841, 900, 961, 1024, 1089, 1156, 1225 etc.

## Square Root Symbol

A square root is written with a radical symbol √ . It is not known where the square root symbol comes from, but its believed it was from the letter r, which is the first letter of the Latin and German word radix. Radix means root or base. Thus, radix quadratum from Latin refer most likely to the base of a square. As the sides of a square are all equal, the word radix may be interpreted as side of a square, even not literally meaning that.