The square root of 1 is 1, just as the square of 1 is 1. The square root of a number finds a result that, when multiplied by itself, equals the original number.
For example, the square root of 4 is 2, because 2 multiplied by itself equals 4. Likewise, the square root of 9 is 3, because 3 multiplied by itself, or squared, equals 9.
The concept of square roots dates back at least 3,600 years, as of 2014, to writing on a Babylonian clay tablet that shows approximate values for the square root of 2 by itself and multiplied by 30. The Egyptians also had a basic understanding of the operation of square roots, as shown by the Rhind Mathematical Papyrus.