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a, \(=\dfrac{1+4}{5}+\dfrac{5+1+3}{9}=1+1=2\)
b, \(=\dfrac{1+4+2}{3}+\dfrac{1+2+5}{6}=\dfrac{6}{3}+\dfrac{8}{6}=2+\dfrac{4}{3}=\dfrac{6+4}{3}=\dfrac{10}{3}\)
1.
=2/5 x 12/3 + 2/5 x 15/3 + 2/5 x 1
= 2/5 x (12/3 + 15/3 + 1)
=2/5 x 1
=2/5
2.a=1;2
\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{5\times4\times13}{13\times5\times3}=\dfrac{4}{3}\\ b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\dfrac{3}{7}\times\dfrac{7}{5}+\dfrac{5}{2}\times\dfrac{7}{5}=\dfrac{3}{5}+\dfrac{7}{2}=\dfrac{6}{10}+\dfrac{35}{10}=\dfrac{41}{10}\\ c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)
a: =20/90+15/90+54/90=89/90
b: =(9/13+4/13)+2/3=1+2/3=5/3
\(\dfrac{4}{7}x\left(\dfrac{2}{5}+\dfrac{3}{5}\right)=\dfrac{4}{7}x1=\dfrac{4}{7}\)
`3/4+2/5+3/12`
`=3/4+3/12+2/5`
`=9/12+3/12+2/5`
`=12/12+2/5`
`=1+2/5`
`=7/5`
dấu . là nhân hay là phần ngăn cách ở hàng phần nghìn thế
\(=\dfrac{17}{2}+\dfrac{3}{5}\times\left(1+\dfrac{1}{2}+1\right)=\dfrac{17}{2}+\dfrac{3}{5}\times\dfrac{5}{2}=\dfrac{17}{2}+\dfrac{15}{10}=\dfrac{17}{2}+\dfrac{3}{2}=\dfrac{17+3}{2}=\dfrac{20}{2}=10\)
\(\dfrac{17}{2}+\dfrac{3}{5}+\dfrac{3}{5}\times\dfrac{1}{2}+\dfrac{3}{5}=\dfrac{17}{2}+\dfrac{3}{5}+\dfrac{3}{10}+\dfrac{3}{5}=\dfrac{85}{10}+\dfrac{6}{10}+\dfrac{3}{10}+\dfrac{6}{10}=10\)