# Bài 84 trang 130 SGK giải tích 12 nâng cao

##### Hướng dẫn giải

\eqalign{ & a)\,{\left( {{2 \over 3}} \right)^p} > {\left( {{3 \over 2}} \right)^{ - q}} \Leftrightarrow {\left( {{2 \over 3}} \right)^p} > {\left( {{2 \over 3}} \right)^q} \Leftrightarrow p < q\,\,\left( {\text{ vì }\,\,\,{2 \over 3} < 1} \right) \cr & b)\,{\left( {{8 \over 3}} \right)^{ - p}} < {\left( {{3 \over 8}} \right)^q} \Leftrightarrow {\left( {{3 \over 8}} \right)^p} < {\left( {{3 \over 8}} \right)^q} \Leftrightarrow p > q\,\,\left( {\text{ vì }\,\,{3 \over 8} < 1} \right) \cr & c)\,\,0,{25^p} < {\left( {{1 \over 2}} \right)^{2q}} \Leftrightarrow {\left( {{1 \over 4}} \right)^p} < {\left( {{1 \over 4}} \right)^q} \Leftrightarrow \,\,p > q\,\,\left( {\text{ vì }\,\,{1 \over 4} < 1} \right) \cr & d)\,\,{\left( {{7 \over 2}} \right)^p} < {\left( {{2 \over 7}} \right)^{p - 2q}} \Leftrightarrow {\left( {{7 \over 2}} \right)^p} < {\left( {{7 \over 2}} \right)^{2q - p}} \Leftrightarrow p < 2q - p\,\,\left( {\text{ vì }\,\,{7 \over 2} > 1} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \Leftrightarrow 2p < 2q \Leftrightarrow p < q \cr}