6. Find these values of the Euler φ-function.a) φ(4) b) φ(10) c) φ(13)7. What are the greatest common divisors of these pairs of integers?a) 37 · 53 · 73, 211 · 35 · 59 b) 11 · 13 · 17, 29 · 37 · 55 · 73 c) 2331, 2317d) 41 · 43 · 53, 41 · 43 · 53 e) 313 · 517, 212 · 721
Question
- Find these values of the Euler φ-function.a) φ(4) b) φ(10) c) φ(13)7. What are the greatest common divisors of these pairs of integers?a) 37 · 53 · 73, 211 · 35 · 59 b) 11 · 13 · 17, 29 · 37 · 55 · 73 c) 2331, 2317d) 41 · 43 · 53, 41 · 43 · 53 e) 313 · 517, 212 · 721
Solution
- The Euler φ-function, also known as Euler's totient function, counts the positive integers up to a given integer n that are relatively prime to n.
a) φ(4): The positive integers less than 4 that are relatively prime to 4 are 1 and 3. So, φ(4) = 2.
b) φ(10): The positive integers less than 10 that are relatively prime to 10 are 1, 3, 7, and 9. So, φ(10) = 4.
c) φ(13): Since 13 is a prime number, all the positive integers less than 13 are relatively prime to 13. So, φ(13) = 12.
- The greatest common divisor (GCD) of two integers is the largest positive integer that divides both numbers without a remainder.
a) GCD(37 · 53 · 73, 211 · 35 · 59): There are no common prime factors, so the GCD is 1.
b) GCD(11 · 13 · 17, 29 · 37 · 55 · 73): There are no common prime factors, so the GCD is 1.
c) GCD(2331, 2317): The GCD is 1 because 2331 and 2317 are prime numbers.
d) GCD(41 · 43 · 53, 41 · 43 · 53): The GCD is the product itself, i.e., 41 · 43 · 53.
e) GCD(313 · 517, 212 · 721): There are no common prime factors, so the GCD is 1.
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