@Thỏ
`A` = $\frac{4^{5}.9^{4} - 2 . 6^{9}}{2^{10}.3^{8}+6^{8}.20}$
`->` `A` = $\frac{2^{10}.3^{8} - 2 . 2^{9}.3^9}{2^{10}.3^{8}+2^{8}.3^8.2^2.5}$
`->` `A` = $\frac{2^{10}.3^{8} - 2^{10}.3^9}{2^{10}.3^{8}+2^{10}.3^8.5}$
`->` `A` = $\frac{2^{10}.3^{8}. (1-3)}{2^{10}.3^{8} . (1+5)}$
`->` `A` = `-2/6` = `-1/3`
