Tính hợp lý: 

- Hướng dẫn giải

$\begin{array}{l}\frac{4^6.9^5+6^9.120}{8^4.3^{12}-6^{11}}=\frac{{\left(2^2\right)}^6.{\left(3^2\right)}^5+2^9{.3}^9{.2}^3\mathrm{.3.5}}{{\left(2^3\right)}^4{.3}^{12}-2^{11}{.3}^{11}}\\ =\frac{2^{12}{.3}^{10}+2^{12}{.3}^{10}.5}{2^{12}{.3}^{12}-2^{11}{.3}^{11}}=\frac{2^{12}{.3}^{10}\left(1+5\right)}{2^{11}{.3}^{11}\left(2.3-1\right)}=\frac{2.6}{3.5}=\frac{4}{5}\end{array}$