Sắp xếp các phân số sau theo thứ tự từ bé đến lớn.
\(\dfrac{-3}{4}\)\(\dfrac{-5}{8}\)\(\dfrac{-3}{14}\)\(\dfrac{9}{28}\)\(\dfrac{4}{7}\)Hướng dẫn giải:BCNN(4, 8, 14, 28, 7) = 56.
\(\dfrac{-3}{4}=\dfrac{\left(-3\right)\cdot14}{4\cdot14}=\dfrac{-42}{56}\); \(\dfrac{-5}{8}=\dfrac{\left(-5\right)\cdot7}{8\cdot7}=\dfrac{-35}{56}\); \(\dfrac{-3}{14}=\dfrac{\left(-3\right)\cdot4}{14\cdot4}=\dfrac{-12}{56}\); \(\dfrac{9}{28}=\dfrac{9\cdot2}{28\cdot2}=\dfrac{18}{56}\); \(\dfrac{4}{7}=\dfrac{4\cdot8}{7\cdot8}=\dfrac{32}{56}\).
Vì \(\dfrac{-42}{56}< \dfrac{-35}{56}< \dfrac{-12}{56}< \dfrac{18}{56}< \dfrac{32}{56}\) nên \(\dfrac{-3}{4}< \dfrac{-5}{8}< \dfrac{-3}{14}< \dfrac{9}{28}< \dfrac{4}{7}\).
