Ta có \[\left[ {{3}^{x+2}}-3 \right]\left[ {{3}^{x}}-y \right]0 \right]\]
Bpt \[\Leftrightarrow \left[ 9t-3 \right]\left[ t-y \right]
Ta có \[\left[ {{3}^{x+2}}-3 \right]\left[ {{3}^{x}}-y \right]0 \right]\]
Bpt \[\Leftrightarrow \left[ 9t-3 \right]\left[ t-y \right]