# Tag Archives: number theory

# Proof: If d|a and d|b, then d|(a-b)

If you’re cheating on your homework, and found this through a websearch, then know your teacher can also find this. Do your own proof.

This is exercise 3.2 of Elementary Number Theory (pdf) by W. Edwin Clark.

We know that and so we write and .

Now which we can also write as . It is now obvious that , q.e.d.