# Math Help - Proofs with prime numbers.

1. ## Proofs with prime numbers.

I'm having a few problems with these questions.

Determine all the twin primes p and q=p+2 for which pq-2 is also prime.

For n>1, show that every prime divisor of n!+1 is an odd integer that is greater than n

2. Originally Posted by MichaelG
I'm having a few problems with these questions.

Determine all the twin primes p and q=p+2 for which pq-2 is also prime.

For n>1, show that every prime divisor of n!+1 is an odd integer that is greater than n

If p,q > 3 then one of them is -1 (mod 3) and the other one is 1 (mod 3) so their product is -1 (mod 3) and thus...

The question about n!+1 is completely trivial if you dive a little deep into the definitions of these things.

Tonio