`text{Ta có}`
`(2.3^{x} - 2^{x + 2})/(3^x - 2^x) <= 1`
`->` $\dfrac{2.(\dfrac{3}{2})^{x} - 2^2}{(\dfrac{3}{2})^{x} - 1}$ `<= 1`
`->` $\dfrac{2.(\dfrac{3}{2})^{x} - 4 - (\dfrac{3}{2})^{x} + 1}{(\dfrac{3}{2})^{x} - 1}$ `<= 0`
`->` $\dfrac{(\dfrac{3}{2})^{x} - 3}{(\dfrac{3}{2})^{x} - 1}$ `<= 0`
`text{Xét 2 trường hợp}`
`+)` \(\left\{ \begin{array}{l}(\dfrac{3}{2})^{x} - 3 ≤ 0\\(\dfrac{3}{2})^{x} - 1 > 0\end{array} \right.\)
`->` \(\left\{ \begin{array}{l}(\dfrac{3}{2})^{x} ≤ 3\\(\dfrac{3}{2})^{x} > 1\end{array} \right.\)
`-> text{vô nghiệm}`
`+)` \(\left\{ \begin{array}{l}(\dfrac{3}{2})^{x} - 3 ≥ 0\\(\dfrac{3}{2})^{x} - 1 < 0\end{array} \right.\)
`->` \(\left\{ \begin{array}{l}(\dfrac{3}{2})^{x} ≥ 3\\(\dfrac{3}{2})^{x} < 1\end{array} \right.\)
`-> 1 < (3/2)^{x} <= 3`
`-> 0 < x <=` $log_{\dfrac{3}{2}} (3)$
`-> x in (0;`$log_{\dfrac{3}{2}} (3)]$
`text{Mà}` `x in ZZ`
`-> x = {1; 2}`
`-> text{Chọn B}`
