Prove that if a is grater than or equal to 2, n is grater than or equal to 2, and (a^n) -1 is prime, then a = 2 and n is a prime.
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Originally Posted by wrighchr Prove that if a is grater than or equal to 2, n is grater than or equal to 2, and (a^n) -1 is prime, then a = 2 and n is a prime. Hint: $\displaystyle x^n - 1 = (x-1)(x^{n-1}+...+x+1)$.
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