\(\lim n\left( {\sqrt {{n^2...

C

- Hướng dẫn giải

\(\begin{array}{l}
\lim n\left( {\sqrt {{n^2} + 1}  - \sqrt {{n^2} - 3} } \right)\\
 = \lim n\frac{{\left( {\sqrt {{n^2} + 1}  - \sqrt {{n^2} - 3} } \right)\left( {\sqrt {{n^2} + 1}  + \sqrt {{n^2} - 3} } \right)}}{{\left( {\sqrt {{n^2} + 1}  + \sqrt {{n^2} - 3} } \right)}}\\
 = \lim n.\frac{4}{{n\left( {\sqrt {1 + \frac{1}{{{n^2}}}}  + \sqrt {1 - \frac{3}{{{n^2}}}} } \right)}} = 2
\end{array}\)