\(lim\frac{1}{\sqrt{n^2+1}-\sqrt{n+2}}=lim\frac{\frac{1}{n}}{\sqrt{1+\frac{1}{n^2}}-\sqrt{\frac{1}{n}+\frac{2}{n^2}}}=\frac{0}{1-0}=0\)
\(lim\left(\sqrt{n^2+2n+2}+n\right)=lim\left[n\left(\sqrt{1+\frac{2}{n}+\frac{2}{n^2}}+1\right)\right]=\infty\left(1+1\right)=+\infty\)