Factorial notation represents the product of all positive integers less than or equal to the given number. For example, 5! = 5 x 4 x 3 x 2 x 1 and 8! = 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1. The document also provides examples of simplifying factorials without a calculator by using properties such as 5! + 4! = 6 x 4! and (k + 1)! + k! = (k + 2)k!.

1. Factorial Notation!
n! reads "n factorial"
5! =
8! =
n! = n(n - 1)(n - 2)(n - 3)...
How about 0! = 1
Likewise, n! = n(n - 1)!
or 8! = 8 · 7!
is a natural number

2. Simplify without a calculator:
Show 5! + 4! = 6 · 4!
Show (k + 1)! + k! = (k + 2)k!