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Prove that for any integer a, a^4 ≡ 0 or 1 (mod 5)

Hello, Quote: Originally Posted by terencet Prove that for any integer a, a^4 ≡ 0 or 1 (mod 5) Test this out If then ? If then ? If then ? If then ? If then ? Otherwise, you can use Fermat's little theorem, which says : for p prime, if a is not a multiple of p, then