I need to derive an error equation for Bohr's model to use in my physics lab this week. I am really bad at calculus, so if anyone can help me that would be really great.

the equation is

(1/lambda)=R[(1/n^2final)-(1/n^2initial)]

I've never had to derive anything like this before. Even if someone could tell me HOW to do it, I'll be happy to do it myself.

Thanks