1. The problem statement, all variables and given/known data This is the equation where i, a, b and c are positive integer. [URL]http://www.icedsolo.com/eq.GIF[/URL] 2. Relevant equations [URL]http://www.icedsolo.com/eq.GIF[/URL] 3. The attempt at a solution The question is, proof whether K is always positive, or it is positive in certain range of a, b, and c. This is urgent for me to have above very difficult question resolved, please help!!!