utkarshgupta 18.05.2014 20:22 If $q$ is not equal to $3$. Then obviously $LHS \equiv 2 (mod 3)$ but $RHS \equiv 1 (mod 3)$ (when $p$ is not equal to $3$) or $RHS \equiv 0 (mod 3)$ Thus a contradiction! Thus $q=3$ and the rest is trivial.