Đáp án:
$\begin{array}{l}
1)\lim \frac{{ - {n^4} + 5{n^3} - 5n}}{{2{n^4} - n + 4}}\\
= \lim \frac{{ - 1 + \frac{5}{n} - \frac{5}{{{n^3}}}}}{{2 - \frac{1}{{{n^3}}} + \frac{4}{{{n^4}}}}}\\
= \frac{{ - 1}}{2}\\
2)\lim \frac{{{2^n} - {5^n}}}{{{3^n} + {5^{n + 1}}}}\\
= \lim \frac{{\frac{{{2^n}}}{{{5^n}}} - 1}}{{\frac{{{3^n}}}{{{5^n}}} + 5}} = - \frac{1}{5}
\end{array}$