Homework Statement
Let p be prime. Show that p ∤ n, where n is a positive integer, iff \phi(np) = (p-1)\phi(n).
Homework Equations
Theorem 1: If p is prime, then \phi(p) = p-1. Conversely, if p is a positive integer with \phi(p) = p-1, then p is prime.
Theorem 2: Let m and n be...