Question

Tính nhanh

\(\dfrac{-7}{15}.\dfrac{11}{13}+\dfrac{7}{15}.\dfrac{-2}{13}+\dfrac{8}{15}\)

\(\dfrac{-4}{11}.\dfrac{2}{5}+\dfrac{6}{11}.\dfrac{\left(-3\right)}{10}\)

Answer 1

a) \(=\dfrac{7}{15}.\left(-\dfrac{11}{13}+-\dfrac{2}{13}\right)+\dfrac{8}{15}\)

\(=\dfrac{7}{15}.\left(-1\right)+\dfrac{8}{15}\)

\(=\dfrac{-7}{15}+\dfrac{8}{15}=\dfrac{1}{15}\)

b) \(=-\dfrac{8}{55}+\dfrac{-9}{55}=-\dfrac{17}{55}\)

Answer 2

`(-7)/15 . 11/13 + 7/15 . (-2)/13 +8/15`

`=7/15 . (-11)/13 + 7/15 . (-2)/13 +8/15`

`=7/15 . [(-11)/13+( (-2)/13)]+8/15`

`=7/15 . (-1)+8/15`

`=(-7)/15+8/15`

`=1/15`

`------------`

`(-4)/11 . 2/5 + 6/11 . (-3)/10`

`=((-4)/11+6/11).(2/5+(-3)/10)`

`=2/11 . (4/10+(-3)/10)`

`=2/11 . (-1)/10`

`=1/11 . (-1)/5`

`=-1/55`

Answer 3

\(=\dfrac{7}{15}.\dfrac{-11}{13}+\dfrac{7}{15}.\dfrac{-2}{13}+\dfrac{8}{15}\)

\(=\dfrac{7}{15}.\left(\dfrac{-11}{13}-\dfrac{2}{13}\right)+\dfrac{8}{15}\)

\(=\dfrac{7}{5}.\left(-1\right)+\dfrac{8}{15}\)

\(=\dfrac{-7}{15}+\dfrac{8}{15}=\dfrac{1}{15}\)

 

Answer 4

\(\dfrac{-7}{15}\cdot\dfrac{11}{13}+\dfrac{7}{15}\cdot\dfrac{-2}{13}+\dfrac{8}{15}=\dfrac{7}{15}\cdot\dfrac{-11}{13}+\dfrac{7}{15}\cdot\dfrac{-2}{13}+\dfrac{8}{15}=\dfrac{7}{15}\cdot\left(\dfrac{-11}{13}+\dfrac{-2}{13}\right)+\dfrac{8}{15}=\dfrac{7}{15}\cdot\left(-1\right)+\dfrac{8}{15}=-\dfrac{7}{15}+\dfrac{8}{15}=\dfrac{1}{15}\)

\(\dfrac{-4}{11}\cdot\dfrac{2}{5}+\dfrac{6}{11}\cdot\left(\dfrac{-3}{10}\right)=-\dfrac{8}{55}+\left(-\dfrac{18}{110}\right)=-\dfrac{16}{110}-\dfrac{18}{110}=-\dfrac{34}{110}=-\dfrac{17}{55}\)