a) \(\dfrac{1}{7}.\dfrac{-3}{8}+\dfrac{1}{7}.\dfrac{-13}{8}\)

\(=\dfrac{1}{7}.\left(\dfrac{-3}{8}+\dfrac{-13}{8}\right)\)

\(=\dfrac{1}{7}.\left(-2\right)\)

\(=\dfrac{-2}{7}\)

b) \(\dfrac{3}{5}.\dfrac{13}{46}-\dfrac{1}{10}.\dfrac{16}{23}\)

\(=\dfrac{39}{230}\) - \(\dfrac{8}{115}\)

\(=\dfrac{1}{10}\)

a, \(\dfrac{1}{7}.\left(-\dfrac{3}{8}\right)+\dfrac{1}{7}.\left(-\dfrac{13}{8}\right)\)

=> \(\dfrac{1}{7}.\left[\left(-\dfrac{3}{8}\right)+\left(-\dfrac{13}{8}\right)\right]\)

=> \(\dfrac{1}{7}.-\dfrac{16}{8}\)

=> \(\dfrac{1}{7}.\left(-2\right)\)

=> \(\dfrac{-2}{7}\)

b/ \(\dfrac{1}{7}\) . ( \(\dfrac{-3}{8}\)) +\(\dfrac{1}{7}\).(\(\dfrac{-13}{8}\))

= \(\dfrac{1}{7}\) . (\(\dfrac{-3}{8}\) + \(\dfrac{-13}{8}\) )

= \(\dfrac{1}{7}\). (-2)

=\(\dfrac{-2}{7}\)

b/ \(\dfrac{3}{5}\).\(\dfrac{13}{46}\)-\(\dfrac{1}{10}\) .\(\dfrac{16}{23}\)

= \(\dfrac{39}{230}\)-\(\dfrac{8}{115}\)

=\(\dfrac{1}{10}\)

bằng 1/7 nha không tên

=27/182 - 1/182 

= 26/182 

= 1/7

bấm máy tính đi :D

= 27/182 - 1/182

= 26/182 

= 1/7

\(a.\frac{1}{7}\times\frac{-3}{8}+\frac{-13}{8}==\frac{-3}{56}+\frac{-13}{8}=\frac{-3}{56}+\frac{-91}{56}=\frac{-94}{56}=\frac{-47}{28}\)

\(b.\frac{3}{5}\times\frac{13}{40}-\frac{1}{10}\times\frac{16}{23}=\frac{39}{200}-\frac{8}{115}=\frac{577}{4600}\)

\(c.\left(\frac{-3}{4}+\frac{2}{5}\right):\frac{3}{7}+\left(\frac{3}{5}+\frac{1}{4}\right):\frac{3}{7}\)

\(=\left(\frac{-3}{4}+\frac{2}{5}\right)\times\frac{7}{3}+\left(\frac{3}{5}+\frac{1}{4}\right)\times\frac{7}{3}\)

\(=\frac{7}{3}\times\left(\frac{-3}{4}+\frac{2}{5}+\frac{3}{5}+\frac{1}{4}\right)\)

\(=\frac{7}{3}\times\left[\left(\frac{-3}{4}+\frac{1}{4}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)\right]\)

\(=\frac{7}{3}\times\left(\frac{-2}{4}+1\right)\)

\(=\frac{7}{3}\times\frac{1}{2}\)

\(=\frac{7}{6}\)

\(d.\frac{7}{8}:\left(\frac{2}{9}-\frac{1}{8}\right)+\frac{7}{8}:\left(\frac{1}{6}-\frac{5}{12}\right)\)

\(=\frac{7}{8}:\frac{7}{72}+\frac{7}{8}:\left(\frac{-1}{4}\right)\)

\(=\frac{7}{8}\times\frac{72}{7}+\frac{7}{8}\times-4\)

\(=\frac{7}{8}\times\left(\frac{72}{7}+\left(-4\right)\right)\)

\(=\frac{7}{8}\times\frac{44}{7}\)

\(=\frac{11}{2}\)

\(\dfrac{3}{7}.\dfrac{9}{36}-\dfrac{1}{14}.\dfrac{1}{13}\)

\(=\dfrac{3.9}{7.36}-\dfrac{1.1}{14.13}\)

\(=\dfrac{3}{28}-\dfrac{1}{182}=\dfrac{37}{364}\)

3/7 . 9/36 - 1/14 . 1/13

= 3/28 - 1/182 

= 37/364

37/364

a) \(\frac{3}{5}\cdot\frac{13}{46}-\frac{1}{10}\cdot\frac{16}{23}=\frac{39-16}{10\cdot23}=\frac{1}{10}\)

b) \(\frac{3}{7}\cdot\frac{9}{26}-\frac{1}{14}\cdot\frac{1}{13}=\frac{27-1}{14\cdot13}=\frac{2\cdot13}{2\cdot7\cdot13}=\frac{1}{7}\)

\(\dfrac{1}{2}\cdot1\cdot\dfrac{1}{3}\cdot10\cdot\dfrac{7}{35}\cdot\dfrac{3}{4}\)

\(=\dfrac{1}{2}\cdot10\cdot\dfrac{1}{5}\cdot1\cdot\dfrac{1}{3}\cdot\dfrac{3}{4}\)

\(=\dfrac{10}{10}\cdot\dfrac{1}{4}=\dfrac{1}{4}\)