Recent content by JLol

So there's this question that has me stuck: The only immunity to viral diseases result from the use of _____. I'm guessing that it's either antibiotics or vaccines, but I'm starting to have doubts. Are my choices correct or should I find another word for the blank?

I know that there are particular formulas for finding the geometric/arithmetic/ and recursive sequences or series with \Sigma. But is there a general formula for finding the sum for all three types? For example, what if I was asked to find a sum of a particular finite sequence but I don't know...