Tìm lim (căn (n^2 +3n +5) -n

* Hướng dẫn giải

$$\begin{gathered} \lim \left(\sqrt{n^2+3n+5}-n\right) \\ =\lim \frac{\left(\sqrt{n^2+3n+5}-n\right)\left(\sqrt{n^2+3n+5}+n\right)}{\sqrt{n^2+3n+5}+n} \\ =\lim \frac{3n+5}{\sqrt{n^2+3n+5}+n}=\lim \frac{3+\frac{5}{n}}{\sqrt{1+\frac{3}{n}+\frac{5}{n^2}}+1}=\frac{3}{2} \end{gathered}$$

Chọn đáp án C