Sum of Two Squares: Is There a Relation?

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SUMMARY

The discussion centers on the mathematical relationship between pairs of integers (a, b) and (m, n) in the context of expressing even numbers as sums of two squares. It establishes that if an even number can be expressed as a² + b², then there are additional relationships such as (a - m)(a + m) = (n - b)(n + b) and (a - n)(a + n) = (m - b)(m + b). Furthermore, it concludes that a prime of the form 1 (mod 4) can be uniquely expressed as a sum of two squares, and an even number can be expressed as such if it is twice a prime of this form or multiplied by a square of a number of form 3 (mod 4).

PREREQUISITES
  • Understanding of number theory concepts, specifically sums of squares.
  • Familiarity with modular arithmetic, particularly mod 4.
  • Knowledge of prime numbers and their classifications.
  • Basic algebraic manipulation of equations involving integers.
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  • Explore the properties of primes of the form 1 (mod 4) and their relation to sums of squares.
  • Study the implications of the theorem on sums of two squares in number theory.
  • Investigate the relationship between even numbers and their representations as sums of two squares.
  • Learn about the generalizations of sums of squares in higher dimensions or other moduli.
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Mathematicians, number theorists, and students interested in advanced topics in algebra and number theory, particularly those focusing on sums of squares and modular arithmetic.

smslca
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sum of two squares?

If an Even number could be expressed in the form a2 + b2 . And if there exits two other numbers m,n such that
a2 + b2 = m2 + n2

then , my question is

is there any relation between (a,b) and (m,n) apart from a2 + b2 = m2 + n2 ??
 
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Well, there is the obvious a^2- m^2= n^2- b^2 so that (a- m)(a+ m)= (n- b)(n+ b).
 


HallsofIvy said:
Well, there is the obvious a^2- m^2= n^2- b^2 so that (a- m)(a+ m)= (n- b)(n+ b).

Or, there is a^2- n^2= m^2- b^2.
 


HallsofIvy said:
Well, there is the obvious a^2- m^2= n^2- b^2 so that (a- m)(a+ m)= (n- b)(n+ b).

configure said:
Or, there is a^2- n^2= m^2- b^2.

So other relations between (a,b) and (m,n) include

(a-m)(a+m) = (n-b)(n+b)

(a-n)(a+n) = (m-b)(m+b)

All of the numbers must solve both of these equations.
 


A prime of form 1 (mod 4) can be uniquely written as sum of two squares.

An even number can be uniquely expressed as a sum of two squares if it is twice a prime of form 1 (mod 4). (or if it is multiplied with any square of number of form 3 (mod 4)).

A number which is product of N distinct primes of form 1 (mod 4) can be represented as sum of two squares in N different ways.
Thus, an even number can be written as sum of two squares in N different ways if it is twice that value (or product of that with any square of number that is equivalent to form 3 (mod 4)).

For more information, please see
refer to this thread.
http://mersenneforum.org/showthread.php?t=13027
 

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