If (p + q) -1 (p -1 + q -1 ) = p a q b , prove that a + b +2 = 0, where p and q are different positive primes.

Given, Substituting values of a and b in L.H.S. of a + b + 2 = 0 we get, a + b + 2 = -1 + (-1) + 2 = -2 + 2 = 0. Hence, proved that a + b + 2 = 0.