sắp xếp các phân số sau theo thứ tự :
a) Tăng dần : \(\dfrac{-5}{6}\) ; \(\dfrac{7}{8}\) ; \(\dfrac{7}{24}\) ; \(\dfrac{16}{17}\) ; \(\dfrac{-3}{4}\) ; \(\dfrac{2}{3}\)
b) giảm dần : \(\dfrac{-5}{8}\) ;\(\dfrac{7}{10}\) ;\(\dfrac{-16}{19}\) ; \(\dfrac{20}{23}\) ;\(\dfrac{214}{315}\) ; \(\dfrac{205}{107}\)
a: \(\dfrac{-5}{6}=\dfrac{-20}{24};\dfrac{7}{8}=\dfrac{21}{24};\dfrac{7}{24}=\dfrac{7}{24};\dfrac{-3}{4}=-\dfrac{18}{24};\dfrac{2}{3}=\dfrac{16}{24}\)
Do đó: \(\dfrac{-5}{6}< -\dfrac{3}{4}< \dfrac{7}{24}< \dfrac{2}{3}< \dfrac{7}{8}\)
\(\dfrac{7}{8}=\dfrac{119}{136};\dfrac{16}{17}=\dfrac{128}{136}\)
mà 119<128
nên 7/8<16/17
DO đó: -5/6<-3/4<7/24<2/3<7/8<16/17
b: \(\dfrac{-5}{8}=\dfrac{-95}{8\cdot19};\dfrac{-16}{19}=\dfrac{-128}{19\cdot8}\)
Do đó: -5/8>-16/19
\(\dfrac{7}{10}=0.7;\dfrac{20}{23}\simeq0.87;\dfrac{214}{315}\simeq0.68;\dfrac{205}{107}>1\)
Do đó: \(\dfrac{205}{107}>\dfrac{20}{23}>\dfrac{7}{10}>\dfrac{214}{315}>-\dfrac{5}{8}>-\dfrac{16}{19}\)
