The question asks you to find the limit of the following sequence $(a_n)$ as $n \rightarrow \infty$.
$a_n = n(\sqrt{n^2+144}-\sqrt{n^2-1})$.
My thoughts were that as n grows $\sqrt{n^2+144}-\sqrt{n^2-1}$ tends to $0$. This is where I got stuck as the n on the outside grows larger. The hints told me that you can do this by using the Algebra of Limits and also the answer is $\frac{145}{2}$.