\(a,\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\times\dfrac{1}{4}=\dfrac{8}{15}\times\dfrac{1}{4}=\dfrac{8}{60}=\dfrac{2}{15}\)
\(\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\times\dfrac{1}{4}=\dfrac{1}{3}\times\dfrac{1}{4}+\dfrac{1}{5}\times\dfrac{1}{4}=\dfrac{1}{12}+\dfrac{1}{20}=\dfrac{20}{240}+\dfrac{12}{240}=\dfrac{32}{240}=\dfrac{2}{15}\)
\(b,\dfrac{2}{5}\times\dfrac{3}{7}+\dfrac{2}{5}\times\dfrac{4}{7}=\dfrac{2}{5}\times\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{2}{5}\times1=\dfrac{2}{5}\)
\(\dfrac{2}{5}\times\dfrac{3}{7}+\dfrac{2}{5}\times\dfrac{4}{7}=\dfrac{6}{35}+\dfrac{8}{35}=\dfrac{14}{35}=\dfrac{2}{5}\)
trả lời nhanh nha! trả lời trong tối hôm nay 19/3/2023 ạ
C1 : `a)(1/3+1/5)xx1/4`
`=(5/15+3/15)xx1/4`
`=8/15xx1/4`
`=8/60`
`=2/15`
__
C2: `a)(1/3+1/5)xx1/4`
`=1/3xx1/4+1/5xx1/4`
`=1/12+1/20`
`=5/60+3/60`
`=8/60`
`=2/15`
_________________
C1: `b)2/5xx3/7+2/5xx4/7`
`=6/35+8/35`
`=14/35`
`=2/5`
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C2: `b)2/5xx3/7+2/5xx4/7`
`=2/5xx(3/7+4/7)`
`=2/5xx7/7`
`=2/5xx1`
`=2/5`
