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Prove the divisibility of the following numbers by 7
[tex]5 {}^{5} - 5 {}^{4} + 5 {} {}^{3} \: [/tex]

Respuesta :

5^5 mod 7 = 3
5^4 mod 7 = 2
5^3 mod 7 = 6

3 -2 +6 mod 7 = 0
Therefore, 5^5 -5^4 +5^3 mod 7 = 0 and that sum is divisible by 7.