Introduction to number theory (Berkeley Math 115) - Introduction to number theory lecture 20. p-adic numbers.

This lecture is part of my Berkeley math 115 course "Introduction to number theory" For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EFj53L8sMbzIhhXSAOpuZ1Fov8 We descibe the general case of Hensel's lemma (or Newton's method) for solving equations, and briefly descibe p-adic numbers. The textbook is "An introduction to the theory of numbers" by Niven, Zuckerman, and Montgomery (5th edition).