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`3/7+2/5+4/7`
`=(3/7+4/7)+2/5`
`=1+2/5`
`=5/5+2/5`
`=7/5`
`20/34+4/9+7/17`
`=(20/34+7/17)+4/9`
`=(20/34+14/34)+4/9`
`=34/34+4/9`
`=1+4/9`
`=9/9+4/9`
`=13/9`
`48xx2+96+48xx6`
`=48xx2+48xx2+48xx6`
`=48xx(2+2+6)`
`=48xx10`
`=480`
câu thứ hai thì làm như này em nhé:
\(\dfrac{20}{34}\) + \(\dfrac{4}{9}\) + \(\dfrac{7}{17}\)
= (\(\dfrac{20}{34}\) + \(\dfrac{7}{17}\)) + \(\dfrac{4}{9}\)
= (\(\dfrac{10}{17}\) + \(\dfrac{7}{17}\)) + \(\dfrac{4}{9}\)
= 1 + \(\dfrac{4}{9}\)
= \(\dfrac{13}{9}\)
bài 1
\(\frac{2}{5}+x=4\) , \(\frac{8}{7}:x=\frac{4}{5}\)
\(\Rightarrow\)\(x=4-\frac{2}{5}\) , \(\Rightarrow\)\(x=\frac{8}{7}:\frac{4}{5}\)
\(\Rightarrow\)\(x=\frac{18}{5}\) , \(\Rightarrow\) \(x=\frac{10}{7}\)
tính cách thuận tiện là dấu = là x vì viết nhầm
\(\frac{5}{9}\times\frac{8}{17}+\frac{4}{9}\times\frac{8}{17}\)
\(=\left(\frac{5}{9}+\frac{4}{9}\right)\times\frac{8}{17}\)
\(=1\times\frac{8}{17}\)
\(=\frac{8}{17}\)
a) 3/7+5/2+4/7
=(3/7+4/7)+5/2
=1+5/2
=7/2
b)6/8+4/5+1/4
=(6/8+1/4)+4/5
=1+4/5
=9/5
đến đó thôi mệt quá
a; \(\dfrac{3}{7}\) + \(\dfrac{5}{2}\) + \(\dfrac{4}{7}\)
= (\(\dfrac{3}{7}+\dfrac{4}{7}\)) + \(\dfrac{5}{2}\)
= 1 + \(\dfrac{5}{2}\)
= \(\dfrac{2}{2}+\dfrac{5}{2}\)
= \(\dfrac{7}{2}\)
b; \(\dfrac{6}{8}\) + \(\dfrac{4}{5}\) + \(\dfrac{1}{4}\)
= \(\dfrac{1}{4}\) + \(\dfrac{4}{5}\) + \(\dfrac{1}{4}\)
= (\(\dfrac{1}{4}\) + \(\dfrac{1}{4}\)) + \(\dfrac{4}{5}\)
= \(\dfrac{2}{4}\) + \(\dfrac{4}{5}\)
= \(\dfrac{1}{2}\) + \(\dfrac{4}{5}\)
= \(\dfrac{5}{10}\) + \(\dfrac{8}{10}\)
= \(\dfrac{13}{10}\)
a. \(\dfrac{17}{13}-\dfrac{14}{23}+\dfrac{9}{13}-\dfrac{9}{23}=\left(\dfrac{17}{13}+\dfrac{9}{13}\right)-\left(\dfrac{14}{23}+\dfrac{9}{23}\right)=\dfrac{26}{13}-\dfrac{23}{23}=2-1=1\)
b.\(\dfrac{49}{5}-\dfrac{1}{2}-\dfrac{1}{4}-\dfrac{1}{32}-\dfrac{1}{16}-\dfrac{1}{32}=\dfrac{49}{5}-\left(1-\dfrac{1}{32}\right)=\dfrac{44}{5}+\dfrac{1}{32}=\dfrac{1413}{160}\)
=(5/9+4/9).8/17
=1.8/17
=8/17
= (5/9 + 4/9) x 8/17
= 1 x 8/17
= 8/17