What is the name of this theorem in Abstract Algebra

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Discussion Overview

The discussion centers around a theorem in Abstract Algebra related to the greatest common divisor (g.c.d) of two integers, specifically the existence of integers \(a\) and \(b\) such that \(ax + by = d\), where \(d\) is the g.c.d of \(x\) and \(y\). Participants explore the theorem's name and its implications, including its relation to the Euclidean algorithm and its significance in number theory.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the theorem is a corollary of the Euclidean algorithm and inquire about its name.
  • One participant identifies the theorem as Bézout's identity.
  • Another participant elaborates that not only do integers \(a\) and \(b\) exist, but \(d\) is minimal among all positive \(\mathbb{Z}\)-linear combinations of \(x\) and \(y\), highlighting the non-uniqueness of \(a\) and \(b\).
  • This participant also notes that the concept leads to the definition of Bezout domains, which share properties with principal ideal domains (PIDs) but are not necessarily Noetherian.
  • There is acknowledgment of the complexity of the information shared, with a suggestion that it may be more than what was initially sought.

Areas of Agreement / Disagreement

Participants generally agree on the identification of the theorem as Bézout's identity, but there is a range of elaboration on its implications and related concepts, indicating a mix of agreement and varying levels of understanding.

Contextual Notes

The discussion includes nuances regarding the uniqueness of \(a\) and \(b\) and the conditions under which Bézout's identity holds, which are not fully resolved.

Amer
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Hi,
There is a theorem in Abstract which said if g.c.d(x,y)= d (g.c.d the greatest common divisor between x and y) then there exist an integers a,b such that

ax + by = d

It is a corollary from Euclidean algorithm.

Does it has a name ?
Thanks in advance.
 
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Amer said:
Hi,
There is a theorem in Abstract which said if g.c.d(x,y)= d (g.c.d the greatest common divisor between x and y) then there exist an integers a,b such that

ax + by = d

It is a corollary from Euclidean algorithm.

Does it has a name ?
Thanks in advance.

In...

Number Theory/Elementary Divisibility - Wikibooks, open books for an open world

... the theorem is indicated simply as 'theorem I'...

Kind regards

$\chi$ $\sigma$
 
Thanks very much, you are great. :D
 
Not only do the integers $a$ and $b$ exist, but furthermore $d$ is minimal among all POSITIVE $\Bbb Z$-linear combinations of $x$ and $y$.

The reason this is important, is because $a,b$ are in general, not unique, but $d$ is. For example:

gcd(4,6) = 2, and we have:

2 = (1)(6) + (-1)(4) but also:

2 = (-5)(6) + (8)(4) (for example).

The Bezout identity is so useful that integral domains in which it holds are given their own name: Bezout domains (this is a slightly stronger condition than any two elements just having a gcd). These domains are "almost PID's (principal ideal domains)", they share many of the same properties of PID's, but do not have to be Noetherian.

Perhaps this is "too much information". Simpler version: there are many kinds of structures in which SOME of the intuitions we have from integers still apply, but not ALL of them.
 
Deveno said:
Not only do the integers $a$ and $b$ exist, but furthermore $d$ is minimal among all POSITIVE $\Bbb Z$-linear combinations of $x$ and $y$.

The reason this is important, is because $a,b$ are in general, not unique, but $d$ is. For example:

gcd(4,6) = 2, and we have:

2 = (1)(6) + (-1)(4) but also:

2 = (-5)(6) + (8)(4) (for example).

The Bezout identity is so useful that integral domains in which it holds are given their own name: Bezout domains (this is a slightly stronger condition than any two elements just having a gcd). These domains are "almost PID's (principal ideal domains)", they share many of the same properties of PID's, but do not have to be Noetherian.

Perhaps this is "too much information". Simpler version: there are many kinds of structures in which SOME of the intuitions we have from integers still apply, but not ALL of them.

Awesome additions, thanks
 
Last edited:

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