Why is the factorial of 0 equal to 1?

Question

Wouldn’t this also mean that 1!=0!, why is this true?

In: 383

Answer 1

Factorial is typically used when figuring out combinations. x! tells you how many ways there are to arrange x objects. there are 0! or 1 way to arrange 0 objects.

There are also people who define factorial recursively for reasons I wont get into here,
so n! = (n-1)! times n. If 0! wasn’t 1 this wouldn’t work anymore.