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\(a:=\left(\dfrac{1}{4}+\dfrac{3}{4}\right)+\left(\dfrac{1}{5}+\dfrac{2}{5}\right)\\ =1+\dfrac{3}{5}=1\dfrac{3}{5}\\ b:=\left(\dfrac{2}{7}+\dfrac{1}{7}\right)+\left(\dfrac{5}{14}+\dfrac{3}{14}\right)\\ =\dfrac{3}{7}+\dfrac{8}{14}\\ =\dfrac{3}{7}+\dfrac{4}{7}=1\)
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\(\frac{1}{2}\cdot\frac{18}{14}+\frac{1}{2}\cdot\frac{3}{14}-\frac{1}{2}\cdot\frac{7}{14}\)
\(=\frac{1}{2}\left(\frac{18}{14}+\frac{3}{14}-\frac{7}{14}\right)\)
\(=\frac{1}{2}\cdot1=\frac{1}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{3}{7}-\dfrac{1}{14}=\dfrac{6}{14}-\dfrac{1}{14}=\dfrac{5}{14}\)
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`7 xx 3/14 -1/14`
`= 21/14 -1/14`
`= 20/14`
`=10/7`
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`3/2 + 7/4 xx 2/5`
`= 3/2 + 14/20`
`= 3/2 + 7/10`
`= 15/10 +7/10`
`= 23/10`
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`9/8 : 3 + 7/3 : 3`
`= 9/8 xx 1/3 + 7/3 xx 1/3`
`=1/3 xx ( 9/8 + 7/3)`
`= 1/3 xx 83/24`
`= 83/72`
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`2 : 3/4 - 5/8 xx 4/3`
`= 2 xx 4/3 - 5/8 xx 4/3`
`= 4/3 xx ( 2-5/8)`
`= 4/3 xx ( 16/8 -5/8)`
`= 4/3 xx 11/8`
`= 44/24`
`=11/6`
` @ \color{Red}{sushiteam}`
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\dfrac{2}{7}+\dfrac{5}{7}.\dfrac{7}{10}-\dfrac{1}{14}\)
\(=\dfrac{1}{7}.2+\dfrac{1}{7}.5.\dfrac{7}{10}-\dfrac{1}{7}.\dfrac{1}{2}\)
\(=\dfrac{1}{7}.\left(2+\dfrac{35}{10}-\dfrac{1}{2}\right)\)
\(=\dfrac{1}{7}.\left(\dfrac{4}{2}+\dfrac{7}{2}-\dfrac{1}{2}\right)\)
\(=\dfrac{1}{7}.5=\dfrac{5}{7}\)
\(b,\left(3\dfrac{1}{2}-\dfrac{2}{3}\right).\dfrac{7}{34}-\dfrac{5}{34}\)
\(=\left(\dfrac{7}{2}-\dfrac{2}{3}\right).\dfrac{7}{34}-\dfrac{7}{34}.\dfrac{5}{7}\)
\(=\dfrac{7}{34}.\left(\dfrac{17}{6}-\dfrac{5}{7}\right)\)
\(=\dfrac{7}{34}.\dfrac{89}{42}=\dfrac{89}{204}\)
a: =2/7-1/14+5/10
=2/7-1/14+1/2
=4/14-1/14+7/14
=10/14=5/7
b: =(7/2-2/3)*7/34-5/34
\(=\dfrac{21-4}{6}\cdot\dfrac{7}{34}-\dfrac{5}{34}\)
\(=\dfrac{7}{6}\cdot\dfrac{1}{2}-\dfrac{5}{34}=\dfrac{7}{12}-\dfrac{5}{34}=\dfrac{89}{204}\)
3/7-1/14
=6/14-1/14
=5/14
_HT_
\(\frac{3}{7}-\frac{1}{14}=\frac{6}{14}-\frac{1}{14}=\frac{5}{14}\)
@muối