divisibility by prime number
Theorem.
Let and be integers and any prime number. Then we have:
(1) |
Proof. Suppose that . Then either or . In the latter case we have , and therefore the corollary of Bézout’s lemma gives the result . Conversely, if or , then for example for some integer ; this implies that , i.e. .
Remark 1. The theorem means, that if a product is divisible by a prime number, then at least one of the factor is divisibe by the prime number. Also conversely.
Remark 2. The condition (1) is expressed in of principal ideals as
(2) |
Here, is a prime ideal of .