題組內容
4.
(a) [5%] For a positive integer n, let Φ(n) denote the cardinality of invertible elements in the ring
Show that
where p runs through all primes dividing n.
(a) [5%] For a positive integer n, let Φ(n) denote the cardinality of invertible elements in the ring
Show that
where p runs through all primes dividing n.