During my last interview session, I was asked on Fibonacci Number. The question is how do I find the n-th number of Fibonacci using equation? For example I was given the 80th number, how do I determine it? Great Mathematician, please show me the exact and complete solution to it. I'm desperate as the next interview is two day from now. Thank you in advance. -=Re-edit=- I just do some homeworks to it and finally I understand part of the solution. However, I'm still poor in the identities. By the way, I also need the solution in Programming C++. Kindly help me with the coding/language. Thank you!