\(\frac{3}{7}.\frac{9}{26}-\frac{1}{14}.\frac{1}{13}\)

\(=6.\frac{1}{14}.\frac{1}{13}.\frac{9}{2}-\frac{1}{14}.\frac{1}{13}\)

\(=\frac{1}{14}.\frac{1}{13}.\left(\frac{6.9}{2}-1\right)\)

\(=\frac{1}{182}.26\)

\(=\frac{1}{7}\)

3/7.9/26-1/14.1/13=3.9/7.26-1/14.1/13

                          =27/182-1/14.1/13

                          =27/182-1.1/14.13

                          =27/182-1/182

                          =26/182=1/7

Đề bài là gì bạn ơi ??

de bai la tinh

\(C=\frac{3}{7}\times\frac{4}{13}+\frac{3}{7}\times\frac{9}{13}+5\frac{4}{7}\)

\(C=\frac{3}{7}\times\frac{4}{13}+\frac{3}{7}\times\frac{9}{13}+\frac{39}{7}\)

\(C=\frac{3}{7}\times\left(\frac{4}{13}+\frac{9}{13}\right)+\frac{39}{7}\)

\(C=\frac{3}{7}\times1+\frac{39}{7}\)

\(C=\frac{3}{7}+\frac{39}{7}\)

\(C=\frac{42}{7}\)

\(C=6\)

_Chúc bạn học tốt_

Cách hai:

A; \(\dfrac{17}{19}\) x \(\dfrac{12}{15}\) x \(\dfrac{19}{17}\)

= \(\dfrac{68}{95}\) x \(\dfrac{19}{17}\)

= \(\dfrac{4}{5}\)

Cách 1:

A. \(\dfrac{17}{19}\) x \(\dfrac{12}{15}\) x \(\dfrac{19}{17}\)

= (\(\dfrac{17}{19}\) x \(\dfrac{19}{17}\)) x \(\dfrac{12}{15}\)

= \(1\) x \(\dfrac{12}{15}\)

= \(\dfrac{4}{5}\)

B; Cách 1: (\(\dfrac{5}{7}\) + \(\dfrac{9}{7}\)) x \(\dfrac{21}{28}\)

                 =  2 x \(\dfrac{3}{4}\)

                 =   \(\dfrac{3}{2}\)

Cách 2:   (\(\dfrac{5}{7}+\dfrac{9}{7}\)) x \(\dfrac{21}{28}\) 

             =  \(\dfrac{5}{7}\) x \(\dfrac{21}{28}\) + \(\dfrac{9}{7}\) x \(\dfrac{21}{28}\)

             =   \(\dfrac{15}{28}\) + \(\dfrac{27}{28}\)

            = \(\dfrac{42}{28}\)

            = \(\dfrac{3}{2}\)

 câu A cách 1 

 \(\dfrac{17}{19}\times\dfrac{12}{15}\times\dfrac{19}{17}\) 

=\(\dfrac{17\times12\times19}{19\times15\times17}\) 

=\(\dfrac{12}{15}\)

câu A cách 2 

\(\dfrac{17}{19}\times\dfrac{12}{15}\times\dfrac{19}{17}\) 

=\(\dfrac{17}{19}\times\dfrac{19}{17}\times\dfrac{12}{15}\) 

=1 x \(\dfrac{12}{15}\) 

=\(\dfrac{12}{15}\)

\(a,\dfrac{7}{9}\times\dfrac{3}{14}:\dfrac{5}{8}=\dfrac{7}{9}\times\dfrac{3}{14}\times\dfrac{8}{5}=\dfrac{4}{15}\)

\(b,\dfrac{3}{5}\times\dfrac{4}{21}\times\dfrac{25}{3}=\dfrac{20}{21}\)

\(c,\dfrac{15}{16}:\dfrac{5}{8}\times\dfrac{3}{4}=\dfrac{15}{16}\times\dfrac{8}{5}\times\dfrac{3}{4}=\dfrac{9}{8}\)

\(d,\dfrac{21}{4}\times\dfrac{16}{14}\times\dfrac{1}{2}\times\dfrac{8}{3}=8\)

3/7 . 9/26 - 1/14 . 1/13 - 1/7=0 nhaaa

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\(\frac{3}{7}\cdot\frac{9}{26}-\frac{1}{14}\cdot\frac{1}{13}-\frac{1}{7}\)

\(=\frac{1}{7}\cdot\frac{27}{26}-\frac{1}{7}\cdot\frac{1}{26}-\frac{1}{7}\)

\(=\frac{1}{7}\cdot\left(\frac{27}{26}-\frac{1}{26}-1\right)\)

\(=\frac{1}{7}\cdot0=0\)

\(a,\dfrac{1}{3}+\dfrac{3}{4}\times\dfrac{2}{9}=\dfrac{1}{3}+\dfrac{6}{36}=\dfrac{1}{3}+\dfrac{1}{6}=\dfrac{2}{6}+\dfrac{1}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)

\(b,2-\left(\dfrac{2}{5}+\dfrac{2}{3}\right)=2-\left(\dfrac{6}{15}+\dfrac{10}{15}\right)=2-\dfrac{16}{15}=\dfrac{30}{15}-\dfrac{16}{15}=\dfrac{14}{15}\)

\(c,\dfrac{2}{5}:\dfrac{4}{7}+\dfrac{1}{3}=\dfrac{2}{5}\times\dfrac{7}{4}+\dfrac{1}{3}=\dfrac{14}{20}+\dfrac{1}{3}=\dfrac{7}{10}+\dfrac{1}{3}=\dfrac{21}{30}+\dfrac{10}{30}=\dfrac{31}{30}\)

\(d,\dfrac{9}{13}:\dfrac{3}{26}-\dfrac{8}{13}=\dfrac{9}{13}\times\dfrac{26}{3}-\dfrac{8}{13}=\dfrac{234}{39}-\dfrac{8}{13}=6-\dfrac{8}{13}=\dfrac{78}{13}-\dfrac{8}{13}=\dfrac{70}{13}\)

a:=1/3+6/36

=1/3+1/6

=1/2

b: =2-16/15

=14/15

c: =2/5*7/4+1/3

=14/20+1/3

=7/10+1/3

=21/30+10/30=31/30

d: =9/13*26/3-8/13

=3-8/13=31/13