Abstract
In this chapter, we will consider the general question of whether an integer a has a square root mod (n), and if so, how many there are and how one can find them. One of the main applications of this is to the solution of quadratic congruences, but we will also deduce a proof that there are infinitely many primes p = 1 mod (4), and we will give a useful primality test for Fermat numbers.
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© 1998 Springer-Verlag London
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Jones, G.A., Jones, J.M. (1998). Quadratic Residues. In: Elementary Number Theory. Springer Undergraduate Mathematics Series. Springer, London. https://doi.org/10.1007/978-1-4471-0613-5_7
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DOI: https://doi.org/10.1007/978-1-4471-0613-5_7
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Publisher Name: Springer, London
Print ISBN: 978-3-540-76197-6
Online ISBN: 978-1-4471-0613-5
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