\(\begin{array}{l}
lim\left( {\sqrt {{n^2} - 1} - \sqrt {{n^2} + 2} } \right)n = lim\frac{{\left( {{n^2} - 1} \right) - \left( {{n^2} + 2} \right)}}{{\sqrt {{n^2} - 1} + \sqrt {{n^2} + 2} }}\\
= lim\frac{{ - 3n}}{{n\sqrt {1 - \frac{1}{{{n^2}}}} + n\sqrt {1 + \frac{2}{{{n^2}}}} }} = - \frac{3}{2}
\end{array}\)
-- Mod Toán 11