I have recently answered this question. However, after my answer the OP made an edit which includes more questions. It says:
EDIT: "some other conditions" has been put in the range of summation in r.h.s. Now I have some other questions:
I can understand having more questions. Should we ask them in comment line, or make an edit in the question or ask a new question?
What is the policy of the site on this? Is it okay to constantly add more questions in your post?