\(\frac{5}{5}x\)\(\frac{17}{21}+\frac{17}{21}x\)\(\frac{2}{5}\)

=(\(\frac{5}{5}+\frac{2}{5}\)) x\(\frac{17}{21}\)

=\(\frac{7}{5}x\)\(\frac{17}{21}\)

\(\frac{119}{105}\)

ko hiểu

 7/5x17/21=17/15 mới đúng

a) 21/11.22/17.68/63

=21/11.11.2/17.17.4/3.21

=21.11.2.17.4/11.17.3.21

=8/3

b) 5/14.7/13.26/25

=5/2.7.7/13.2.13/5.5

=5.7.2.13/2.7.13.5.5

=1/5

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Nhanh rồi mình tích cho

a: \(\dfrac{6}{7}\cdot\dfrac{16}{15}\cdot\dfrac{7}{6}\cdot\dfrac{21}{32}=\dfrac{16}{32}\cdot\dfrac{21}{15}=\dfrac{1}{2}\cdot\dfrac{7}{5}=\dfrac{7}{10}\)

b: \(\dfrac{21}{17}\cdot\dfrac{13}{14}\cdot56\cdot\dfrac{3}{42}=\dfrac{21}{14}\cdot\dfrac{13}{17}\cdot\dfrac{1}{14}\cdot56=\dfrac{78}{17}\)

c: \(=\dfrac{11}{21}\left(\dfrac{7}{4}+\dfrac{5}{4}\right)=\dfrac{11}{21}\cdot3=\dfrac{11}{7}\)

2/5*(17/21+17/21)=2/5*34/21=68/105

\(\frac{1}{7}x\frac{3}{5}+\frac{3}{5}x\frac{1}{2}+\frac{3}{5}\)

\(=\frac{3}{5}.\left(\frac{1}{7}+\frac{1}{2}+1\right)\)

\(=\frac{3}{5}x\left(\frac{2}{14}+\frac{7}{14}+\frac{14}{14}\right)\)

\(=\frac{3}{5}x\frac{23}{14}\)

\(=\frac{69}{70}\)

Tham khảo nha !!! 

 36-4x9 = 36 - 36 = 0 Vì số nào nhân với 0 thì cũng bằng 0 nên phép tính đó bằng 0

17/35 nhân 9/5 nhân 4/5 

= 17/35 nhân ( 9/5 nhân 4/5 )

= 17/35 nhân 13/5

=  221/175