Đáp án:
$\begin{array}{l}
{I_{23}} = \lim \frac{{{3^{n + 2}} - {{3.5}^{n + 3}}}}{{{{7.2}^{2n + 6}} + {{2.5}^{n + 1}}}}\\
= \lim \frac{{{{9.3}^n} - {{3.5}^3}{{.5}^n}}}{{{{7.4}^n}{{.2}^6} + {{2.5.5}^n}}}\\
= \lim \frac{{9.{{\left( {\frac{3}{5}} \right)}^n} - {{3.5}^3}}}{{{{7.2}^6}.{{\left( {\frac{4}{5}} \right)}^n} + 2.5}}\\
= - \frac{{{{3.5}^3}}}{{2.5}} = - \frac{{75}}{2}
\end{array}$
