Answer
calculate n! by
multiplying all positive integers from $n$ down through 1.
Work Step by Step
See p.709:
If $n$ is a positive integer, the notation $n!$ (read $n$ factorial'') is the product of all positive integers from $n$ down through 1.
$n!=n(n-1)(n-2)\cdots(3)(2)(1)$
Note: $0!$ (zero factorial), by definition, is 1.
$0!=1$
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If n is a positive integer (it is not zero, then), calculate n! by
multiplying all positive integers from $n$ down through 1.
