Difference between revisions of "Relatively prime"

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Two positive [[integer | integers]] <math>{m}</math> and <math>{n}</math> are said to be '''relatively prime''' or ''coprime'' if they share no [[common divisor | common divisors]] greater than 1, so <math>\gcd(m,n)=1</math>. Equivalently, <math>{m}</math> and <math>{n}</math> must have no [[prime]] divisors in common. For example, 15 and 14 are relatively prime: the [[prime factorization]] of 15 is <math>3 \cdot 5</math>, the prime factorization of 14 is <math>2 \cdot 7</math>, and no prime factors are shared between the two.
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Two positive [[integer | integers]] <math>{m}</math> and <math>{n}</math> are said to be '''relatively prime''' or ''coprime'' if they share no [[common divisor | common divisors]] greater than 1. Equivalently, <math>{m}</math> and <math>{n}</math> must have no [[prime]] divisors in common, which is mathematically written <math>\gcd(m,n)=1</math>. The positive integers <math>{m}</math> and <math>{n}</math> are relatively prime if and only if <math>\frac{m}{n}</math> is in lowest terms.
  
Note that positive integers <math>{m}</math> and <math>{n}</math> are relatively prime if and only if <math>\frac{m}{n}</math> is in lowest terms.
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== Number Theory ==
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Relatively prime numbers show up frequently in [[number theory]] formulas and derivations:
  
Relatively prime numbers show up frequently in [[number theory]] formulas and derivations.  [[Euler's totient function]], for example, determines the number of positive integers less than any given positive integer that are relatively prime to that number. The [[Chicken McNugget Theorem]] also involves relatively prime numbers.
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[[Euler's totient function]] determines the number of positive integers less than any given positive integer that are relatively prime to that number.
  
It is also worth noting that by the [[Euclidean algorithm]], consecutive positive integers are always relatively prime. This is related to the fact that two numbers <math>{a}</math> and <math>b</math> are relatively prime if and only if there exist some <math>{x},{y}\in \mathbb{Z}</math> such that <math>ax+by=1</math>.
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By the [[Euclidean algorithm]], consecutive positive integers are always relatively prime. This is related to the fact that two numbers <math>a</math> and <math>b</math> are relatively prime if and only if there exist some <math>{x},{y}\in \mathbb{Z}</math> such that <math>ax+by=1</math>.
  
 
== See also ==
 
== See also ==
 
 
* [[Number theory]]
 
* [[Number theory]]
 
* [[Greatest common divisor]]
 
* [[Greatest common divisor]]
* [[Euclidean algorithm]]
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* [[Chicken McNugget Theorem]]
* [[Euler's totient function]]
 
  
 
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[[Category:Definition]]
 
[[Category:Definition]]
 
[[Category:Number theory]]
 
[[Category:Number theory]]

Revision as of 12:55, 17 April 2008

Two positive integers ${m}$ and ${n}$ are said to be relatively prime or coprime if they share no common divisors greater than 1. Equivalently, ${m}$ and ${n}$ must have no prime divisors in common, which is mathematically written $\gcd(m,n)=1$. The positive integers ${m}$ and ${n}$ are relatively prime if and only if $\frac{m}{n}$ is in lowest terms.

Number Theory

Relatively prime numbers show up frequently in number theory formulas and derivations:

Euler's totient function determines the number of positive integers less than any given positive integer that are relatively prime to that number.

By the Euclidean algorithm, consecutive positive integers are always relatively prime. This is related to the fact that two numbers $a$ and $b$ are relatively prime if and only if there exist some ${x},{y}\in \mathbb{Z}$ such that $ax+by=1$.

See also

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