\(\lim_{n\to\infty}\left\lbrack n\cdot\left(\sqrt{n^2-1}-\sqrt{n^2+2}\right)\right\rbrack\)
\(=\lim_{n\to\infty}\left\lbrack n\cdot\frac{n^2-1-n^2-2}{\sqrt{n^2-1}+\sqrt{n^2+2}}\right\rbrack=\lim_{n\to\infty}\left\lbrack\frac{-3n}{\sqrt{n^2-1}+\sqrt{n^2+2}}\right\rbrack\)
\(=\lim_{n\to\infty}\frac{-3}{\sqrt{1-\frac{1}{n^2}}+\sqrt{1+\frac{2}{n^2}}}=-\frac32\)