# Factorial

## Introduction

The factorial of a nonnegative integer, n, is denoted by: n! and represents the product of all the positive integers less than or equal to n. By definition, 0!=1 and 1!=1.

Example: Find 5!

Solution:

5! = (5)(4)(3)(2)(1)

= 120

Example: Find 10!

Solution:

10! = (10)(9)(8)...(3)(2)(1)

= 3628800

Why is this important?

You might encounter factorials when studying probability, Taylor series (in a calculus class), or in a discrete mathematics course.