a) \(\dfrac{67}{77}=\dfrac{67\cdot83}{77\cdot83}=\dfrac{5561}{6391}\)
\(\dfrac{73}{83}=\dfrac{73\cdot77}{83\cdot77}=\dfrac{5621}{6391}\)
mà 5561<5621
nên \(\dfrac{67}{77}< \dfrac{73}{83}\)
b) \(\dfrac{456}{461}-1=\dfrac{-5}{461}\)
\(\dfrac{123}{128}-1=\dfrac{-5}{128}\)
mà 461>128
nên \(\dfrac{456}{461}>\dfrac{123}{128}\)