Residues and non residues of general quadratic congruences

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SUMMARY

The discussion focuses on solving the quadratic congruence ax² + bx + c ≡ 0 (mod n) where n is composite and (4a, n) = 1. The key transformation involves rewriting the equation as (2ax + b)² ≡ b² - 4ac (mod n), leading to the equivalence y² ≡ z (mod n). The participants explore the existence of residues and non-residues as z values for various ranges of x in Zn, questioning whether there are ranges that yield only residues or only non-residues.

PREREQUISITES
  • Understanding of quadratic congruences
  • Familiarity with modular arithmetic
  • Knowledge of composite numbers and their properties
  • Experience with residue classes in number theory
NEXT STEPS
  • Study the properties of quadratic residues and non-residues in modular arithmetic
  • Learn about the Chinese Remainder Theorem and its applications in solving congruences
  • Investigate the implications of (4a, n) = 1 in quadratic equations
  • Explore advanced topics in number theory, such as the Legendre symbol and its applications
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Mathematicians, number theorists, and students studying modular arithmetic and quadratic congruences will benefit from this discussion.

smslca
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for a given range of x in Zn , and n is composite , and ax² + bx + c ≡ 0(mod n) and if (4a,n)=1,
I learned that we can solve the congruence by (2ax + b)² ≡ b²-4ac (mod n) ==> y² ≡ z (mod n)

So, if n is composite,

Sometimes I see, modulo 4an, when do we take 4an and n ,

how can we prove , there exists residues and non-residues as z values. for any range of x in Zn
Is there any range of x in general , such that there exists only either residues or non residues as solutions.

If i am wrong or obscure any where in my question , hope will be notified to me.
 
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