\(a,\dfrac{2}{3}\&\dfrac{3}{4}\)
\(\dfrac{2}{3}=\dfrac{2.4}{3.4}=\dfrac{8}{12}\) ; \(\dfrac{3}{4}=\dfrac{3.3}{4.3}=\dfrac{9}{12}\)
Vì \(\dfrac{8}{12}< \dfrac{9}{12}\)
\(\Rightarrow\dfrac{2}{3}< \dfrac{3}{4}\)
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\(b,\dfrac{4}{-5}\&\dfrac{-8}{9}\)
\(\dfrac{4}{-5}=\dfrac{4.9}{-5.9}=\dfrac{-36}{45}\) ; \(\dfrac{-8}{9}=\dfrac{-8.5}{9.5}=\dfrac{-40}{45}\)
Vì \(\dfrac{-36}{45}>\dfrac{-40}{45}\)
\(\Rightarrow\dfrac{4}{-5}>\dfrac{-8}{9}\)
`MSC:12`
ta có : `2/3=(2xx4)/(3xx4)=8/12 ; 3/4=(3xx3)/(4xx3)=9/12`
`--------------------`
`MSC:-45`
ta có : \(\dfrac{4}{-5}=\dfrac{4\times9}{-5\times9}=\dfrac{36}{-45};-\dfrac{8}{9}=\dfrac{-8\times\left(-5\right)}{9\times\left(-5\right)}=\dfrac{40}{-45}\)
