number theory prime numbers

woody gooner

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Nov 2, 2009
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1
Im really puzzled as to how to work out the following 2 questions:

1. Find all the prime numbers p (if there are any) for which p^2 -1 is also prime

2. Find all prime numbers p such that p+2 and p+4 are also prime, giving reasons for your answer

Any help would be much appreciated, thanks
 
woody gooner said:
Im really puzzled as to how to work out the following 2 questions:

1. Find all the prime numbers p (if there are any) for which p^2 -1 is also prime <<< Can you factorize that?

2. Find all prime numbers p such that p+2 and p+4 are also prime, giving reasons for your answer

Any help would be much appreciated, thanks
 
For the second one, use the fact that 3 will divide one of any 3 consecutive integers.
 
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