Bài `1`
`a, 36/72=(36:36)/(72:36)= 1/2`
`b,15/125=(15:5)/(125:5)=3/25`
Bài `2`
`a, MSC:36`
`4/9=(4xx4)/(9xx4)=16/36`
`5/4=(5xx9)/(4xx9)=45/36`
`b,MSC:100`
`25/100` giữ nguyên
`20/50=(20xx2)/(50xx2)=40/100`
`c,MSC:45`
`5/9=(5xx5)/(9xx5)=25/45`
`4/5=(4xx9)/(5xx9)=36/45`
`5/3=(5xx15)/(3xx15)=75/45`
\(1.\\ a,\dfrac{36}{72}=\dfrac{36:36}{72:36}=\dfrac{1}{2}\\ b,\dfrac{15}{125}=\dfrac{15:5}{125:5}=\dfrac{3}{25}\\2.\\ a,\dfrac{4}{9}=\dfrac{4\times4}{9\times4}=\dfrac{16}{36}\\ \dfrac{5}{4}=\dfrac{5\times9}{4\times9}=\dfrac{45}{36}\\ b,\dfrac{25}{100}giữnguyên\\ \dfrac{20}{50}=\dfrac{20\times2}{50\times2}=\dfrac{40}{100}\\ c,\dfrac{5}{9}=\dfrac{5\times5}{9\times5}=\dfrac{25}{45}\\ \dfrac{4}{5}=\dfrac{4\times9}{5\times9}=\dfrac{36}{45}\\ \dfrac{5}{3}=\dfrac{5\times15}{3\times15}=\dfrac{75}{45}\)
