SOLUTION: proof of zero factorial

Question 378803: proof of zero factorial
Found 2 solutions by rapaljer, robertb:
Answer by rapaljer(4671) (Show Source): You can put this solution on YOUR website!
You can't PROVE that 0! is 1. 0!=1 by DEFINITION. There is no proof.

Dr. Rapalje
Answer by robertb(5830) (Show Source): You can put this solution on YOUR website!
0! = 1.
This is not a proof, but just an explanation. The number of ways of selecting r objects out of n objects regardless of order, , is given by . If r = n, it is equivalent to selecting all objects at one time. The number of ways of doing that is 1. Hence , or , or . Thus 0! = 1.
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