Mẫu số chung : \(35\)
\(\dfrac{2}{5}=\dfrac{2.7}{5.7}=\dfrac{14}{35}\\ \dfrac{3}{7}=\dfrac{3.5}{5.7}=\dfrac{15}{35}\)
\(\dfrac{2}{5}=\dfrac{14}{35}\); \(\dfrac{3}{7}=\dfrac{15}{35}.\)
ta có
`MSC:35`
`2/5=(2xx7)/(5xx7)=14/35`
`3/7=(3xx5)/(7xx5)=15/35`