Introduction to number theory (Berkeley Math 115) - Introduction to number theory lecture 3: Divisibility and Euclid's algorithms.

This lecture is part of my Berkeley math 115 course "Introduction to number theory" The lecture covers basic properties of divisibility, and Euclid's algorithm for finding greatest common divisors. For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EFj53L8sMbzIhhXSAOpuZ1Fov8 The textbook is "An introduction to the theory of numbers" by Niven, Zuckerman, and Montgomery (5th edition).