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Proggy99
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Homework Statement
If n>4 is a composite number, show that n|(n-1)! Conclude that (n-1)! not congruent -1(mod n).
(This shows that Wilson's theorem can be used as a proof of primality. It is unfortunately not practical for large numbers)
Homework Equations
The Attempt at a Solution
I know in words why a composite (ab) number does not work, but am not really sure how to prove it. Can anyone give me a jumping off point for this problem please?