Prove that $n^4−1 $ is divisible by 5 when n is not divisible by 5.

Asked Jan 05 '15 at 22:09

Active Jan 14 '15 at 20:17

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Apparently the easiest method is to use proof by exhaustion, but I've no idea how. Any ideas/solutions?
Prove that $n^4−1$ is divisible by 5 when n is not divisible by 5.

edited Jan 14 '15 at 20:17

Martin Sleziak

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asked Jan 05 '15 at 22:09

mathsnub

Prove that $n^4−1 $ is divisible by 5 when n is not divisible by 5.

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