Use the epsilon-n_{0}definition of convergence of a sequence to prove that $\displaystyle \lim_{n \rightarrow \infty } \frac{ {a}^2_{n} -1 }{{a}^2_{n} +1}} $ = L ∈ ℝ.

I'm very new to epsilon-n_{0 }proofs. Can someone help me get started? I substituted L for the actual value of the limit as I'm waiting to see what the actual value is (not sure if it can be in terms of L).