Cho \(A =  - \frac{5}{6}.\frac{{12}}{{ - 7}}.\left( {\frac{{ - 21}}{{15}}} \right);B = \frac{1}{6}.

* Hướng dẫn giải

\(\begin{array}{l}
A =  - \frac{5}{6}.\frac{{12}}{{ - 7}}.\left( {\frac{{ - 21}}{{15}}} \right) =  - 2;B = \frac{1}{6}.\frac{9}{{ - 8}}\left( {\frac{{ - 12}}{{11}}} \right) = \frac{9}{{44}}\\
 \Rightarrow A < B
\end{array}\)