|
In mathematics, a number q is called a quadratic
residue modulo p if there exists an integer x such that:
-
Otherwise, q is called a quadratic non-residue.
In effect, a quadratic residue modulo p is a number that has a square
root in modular arithmetic when the modulus is p.
The Law of quadratic reciprocity says
something about quadratic residues and primes.
Quadratic residues are used in the Legendre symbol. Quadratic reciprocity and the Lemma of Gauss both reason about quadratic residues.
External links
|