Show that if is prime, then must be prime
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Originally Posted by maximus101 Show that if is prime, then must be prime I recommend proving the "contrapositive". Assume p is NOT prime and show that is not prime. It will help to use . You can't apply that to directly because, taking x= 2, x- 1= 2- 1= 1 so that's not a new factor.
Last edited by HallsofIvy; October 18th 2012 at 02:09 PM.
Another related question, prove that 2^2k - 1 is divisible by 3 always. Salahuddin Maths online
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