$\textit{Đáp án + Giải thích các bước giải:}$
$\text{$\dfrac{9^{15} . (-6)^{30}}{27^{21} . 8^{11}}$}$
$\text{= $\dfrac{9^{15} . 6^{30}}{27^{21} . 8^{11}}$ (do $(-6)^{30}$ có số mũ chẵn)}$
$\text{= $\dfrac{(3^2)^{15} . 2^{30} . (3^{30}}{(3^3)^{21} . 8^{11}}$}$
$\text{= $\dfrac{3^{30} . 8^{10} . 3^{30}}{27^{21} . 8^{11}}$}$
$\text{= $\dfrac{3^{60}. 8^{10}}{3^{63} . 8^{11}}$}$
$\text{= $\dfrac{1}{3^3 . 8}$}$
$\text{= $\dfrac{1}{216}$}$
