Prove: If a positive integer n is not prime, then 2^(n)-1 is not prime. If n is not prime, then it factors into n = a*b. Use the identity x^(b) = (x-1)(x^(b-1) + x^(b-2) + ...+ x + 1) and substitute x = 2^(a).
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Originally Posted by noles2188 Prove: If a positive integer n is not prime, then 2^(n)-1 is not prime. If n is not prime, then it factors into n = a*b. Use the identityx^(b) = (x-1)(x^(b-1) + x^(b-2) + ...+ x + 1) and substitute x = 2^(a). There's a "-1" missing in that identity. It should be . Substitute in that and you should have no trouble getting the result.
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