\(A)-\dfrac{7}{18}\) và \(-\dfrac{5}{12}\)
\(+)-\dfrac{7}{18}=-\dfrac{14}{36};-\dfrac{5}{12}=-\dfrac{15}{36}\)
\(+)14< 15\Rightarrow-\dfrac{14}{36}>-\dfrac{15}{36}\Rightarrow-\dfrac{7}{18}>-\dfrac{5}{15}\)
Vậy \(-\dfrac{7}{18}>-\dfrac{5}{12}\)
\(B)\dfrac{123}{-124}\) và \(\dfrac{-310}{311}\)
Ta có: \(1-\dfrac{123}{124}=\dfrac{1}{124}\)\(;1-\dfrac{310}{311}=\dfrac{1}{311}\)
Có: \(\dfrac{1}{124}>\dfrac{1}{311}\Leftrightarrow1-\dfrac{123}{124}>1-\dfrac{310}{311}\)\(\Leftrightarrow1+\left(-\dfrac{123}{124}\right)>1+\left(-\dfrac{310}{311}\right)\Leftrightarrow-\dfrac{123}{124}>-\dfrac{310}{311}\)
Hay \(\dfrac{123}{-124}>\dfrac{-310}{311}\)
Vậy \(\dfrac{123}{-124}>\dfrac{-310}{311}\)
