Number theory: simple gcd question

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SUMMARY

The discussion centers on the mathematical statement that if \( ax + by = 1 \), then the greatest common divisor (gcd) of \( a \) and \( b \) is 1, denoted as \( (a, b) = 1 \). A user presents a proof by contradiction, assuming \( (a, b) = c \) where \( c > 1 \) and demonstrating that this leads to a contradiction since \( c \) must divide 1. The proof is confirmed as valid by other participants, affirming the correctness of the initial statement regarding gcd.

PREREQUISITES
  • Understanding of basic number theory concepts, particularly gcd.
  • Familiarity with linear Diophantine equations.
  • Knowledge of proof techniques, especially proof by contradiction.
  • Basic algebraic manipulation skills.
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  • Study the properties of gcd and their implications in number theory.
  • Learn about linear combinations and their role in solving Diophantine equations.
  • Explore more advanced proof techniques in mathematics.
  • Investigate applications of gcd in cryptography and computer science.
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Students of mathematics, particularly those studying number theory, as well as educators and anyone interested in understanding proofs related to gcd and linear equations.

doubleaxel195
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Homework Statement


If ax+by=1, then (a,b)=1.


Homework Equations





The Attempt at a Solution



I am just wondering if this is true. Because I know it is not true if ax+by=c, then (a,b)=c.

Here is a proof I came up with:

Suppose (a,b)=c, c>1.Then c|a and c|b, but then from our assumption, this implies that c|1, a contradiction.

I'm new to writing proofs so I just want to make sure I am on the right track. Thanks.
 
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