section_path: Definition and notation/Square roots
section_name: Square roots
paragraph_text: Square roots
  
  A square root of a number x is a number r which, when squared, becomes x:
  
  r 2 = x. {\displaystyle r^{2}=x.}
  
  Every positive real number has two square roots, one positive and one negative. For example, the two square roots of 25 are 5 and −5. The positive square root is also known as the principal square root, and is denoted with a radical sign:
  
  25 = 5. {\displaystyle {\sqrt {25}}=5.}
  
  Since the square of every real number is nonnegative, negative numbers do not have real square roots. However, for every negative real number there are two imaginary square roots. For example, the square roots of −25 are 5 i and −5 i, where i represents a number whose square is −1.