Factorial Notation

I introduce the Factorial Notation or symbol. I then work through a number of examples of how to evaluate factorials, and examples of factorials in sequence notation and summation notation. For all my lessons on Sequences and Series go here:) http://www.profrobbob.com/pre-calculus/intro-to-sequences-arithmetic-geometric From Impuhlz: (Thanks) 0! is 1 because you can arrange 0 things in one possible way. You can arrange 1 thing in 1 possible way, which is why 1! = 1. You can arrange 2 things in 2 possible ways, which is why 2! = 2. You can arrange 3 things in 6 possible ways, which is why 3! = 6, ect. It's all about those permutations! Btw I learned this in my programming class, because it's relevant to how many times certain data needs to be checked in order for a program to run, and you run into very slow and inefficient programs when you have a program checking data in the order of n!. Hope I helped anyone confused about why 0! = 1. :) Check out http://www.ProfRobBob.com/, there you will find my lessons organized by class/subject and then by topics within each class. Find free review test, useful notes and more at http://www.mathplane.com/ If you'd like to make a donation to support my efforts look for the "Tip the Teacher" button on my channel's homepage    / profrobbob