Q: Let p and q be prime numbers. Prove that pq + 1 is a square if and only if p and q are twin primes.

(<=)

Pf: p and q are twin primes (i.e. - p = q+2)

Therefore, pq+1 = q(q+2) +1 = q^2 + 2*q +1 = (q+1)^2

(=>)

This is where I'm stuck.

Pf: (By Contradiction?)

What is a way to show that p and q are not twin primes?

Is it something like p-q > 2?

How would I use something like that to form a contradiction?