`a,` vì `5<8->5/15<8/15`
`b,8/9=(8xx5)/(9xx5)=40/45`
`->16/45<8/9`
`c,4/5=(4xx4)/(5xx4)=16/20`
`5/4=(5xx5)/(4xx5)=25/20`
`->4/5<5/4`
`d,9/12=(9xx13)/(12xx13)=117/156`
`8/13=(8xx12)/(13xx12)=96/156`
`-> 9/12>8/13`
\(a,\dfrac{5}{15}...\dfrac{8}{15};5< 8\rightarrow\dfrac{5}{15}< \dfrac{8}{15}\)
\(b,\dfrac{16}{45}...\dfrac{8}{9};\dfrac{16}{45}=\dfrac{16}{45};\dfrac{8}{9}=\dfrac{8\times5}{9\times5}=\dfrac{40}{45};16< 40\rightarrow\dfrac{16}{45}< \dfrac{8}{9}\)
\(c,\dfrac{4}{5}...\dfrac{5}{4};\dfrac{4}{5}=\dfrac{4\times4}{5\times4}=\dfrac{16}{20};\dfrac{5}{4}=\dfrac{5\times5}{4\times5}=\dfrac{25}{20};16< 25\rightarrow\dfrac{4}{5}< \dfrac{5}{4}\)
\(d,\dfrac{9}{12}...\dfrac{8}{13};\dfrac{9}{12}=\dfrac{9\times13}{12\times13}=\dfrac{117}{156};\dfrac{8}{13}=\dfrac{8\times12}{13\times12}=\dfrac{96}{156};117>96\rightarrow\dfrac{9}{12}>\dfrac{8}{13}\)
a) \(\dfrac{5}{15}< \dfrac{8}{15}\)
b) \(\dfrac{16}{45}< \dfrac{8}{9}\)
c) \(\dfrac{4}{5}=\dfrac{5}{4}\)
d) \(\dfrac{9}{12}>\dfrac{8}{13}\)
