Two numbers are said to be ‘relatively prime’ if their greatest common factor is 1
2 and 9 are relatively prime. Because they share no common factors:
- 2: factors
[1, 2]
- 9: factors
[1, 3, 9]
No number other than “1” is shared. Therefore they are, by definition, relatively prime.
9 and 27 are not relatively prime, because their Greatest Common Factor is > 1 (it’s 3).