Question

1. Tính:

-5/7 - 3/14 + 11/21

-5/21 + 9/28 

Answer 1

\(-\dfrac{5}{7}-\dfrac{3}{14}+\dfrac{11}{21}=-\dfrac{30}{42}-\dfrac{9}{42}+\dfrac{22}{42}=-\dfrac{17}{42}\)

\(-\dfrac{5}{21}+\dfrac{9}{28}=-\dfrac{20}{84}+\dfrac{27}{84}=\dfrac{7}{84}=\dfrac{1}{12}\)

 

Answer 2

`(-5)/7 - 3/14 + 11/21`

`=(-30)/42 - 9/42 + 22/42`

`=(-30 -9+22)/42`

`=(-17)/42`

______________________________

`(-5)/21 + 9/28`

`=(-20)/84 + 27/84`

`=(-20 +27)/84`

`=7/84`

`=1/12`