Hi all. I am getting into the chain rule in my Calculus with Matrices business course. I've come across a problem, our system is all online, and i cannt figure it out. They examples they provided were pretty simple and staight forward, but i cannot put htis one together. I'm sure its really easy, but i'd appreciate it if someone would explain

If f(x)=$\displaystyle \frac{1}{X^2 +1}$

then f '(x) is what? The system tell me the answer is $\displaystyle \frac{-2X}{(X^2+1)^2}$

I cannot figure out even where to start on this problem nor which derivative rule to use. I'm probably overcomplicating it, but if any one would be willing to help i'd greatly appreciate it!