Tìm lim (căn (2n+1)- căn (n+3))/ căn (4n-5)

* Hướng dẫn giải

$$\begin{gathered} \lim \frac{\sqrt{2n+1}-\sqrt{n+3}}{\sqrt{4n-5}}=\lim \frac{\sqrt{n}.\sqrt{2+\frac{1}{n}}-\sqrt{n}.\sqrt{1+\frac{3}{n}}}{\sqrt{n}.\sqrt{4-\frac{5}{n}}} \\ =\lim \frac{\sqrt{2+\frac{1}{n}}-\sqrt{1+\frac{3}{n}}}{\sqrt{4-\frac{5}{n}}}=\frac{\sqrt{2}-1}{2} \end{gathered}$$

Chọn đáp án C