\(\left(-\dfrac{2}{3}+\dfrac{3}{7}\right):\dfrac{4}{5}+\left(-\dfrac{1}{3}+\dfrac{4}{7}\right)+\dfrac{4}{5}\\ =-\dfrac{5}{21}:\dfrac{4}{5}+\dfrac{5}{21}\\ =\left(-\dfrac{5}{21}+\dfrac{5}{21}\right):\dfrac{4}{5}\\ =0:\dfrac{4}{5}\\ =0.\)
Sửa cho mk dòng đầu là :4/5 và dòng tiếp theo mk thiếu :4/5
`#040911`
\((\dfrac{-2}{3} + \dfrac{3}{7}) \div \dfrac{4}{5} + (\dfrac{-1}{3} + \dfrac{4}{7}) \div \dfrac{4}{5} \)
\(=(\dfrac{-2}{3} + \dfrac{3}{7}) . \dfrac{5}{4} + (\dfrac{-1}{3} + \dfrac{4}{7}) . \dfrac{5}{4}\)
\(= \dfrac{5}{4} . (\dfrac{-2}{3} + \dfrac{3}{7} - \dfrac{1}{3} + \dfrac{4}{7})\)
\(= \dfrac{5}{4} . [ (\dfrac{-2}{3} - \dfrac{1}{3}) + (\dfrac{3}{7} + \dfrac{4}{7})] \)
\(= \dfrac{5}{4} . ( - 1 + 1)\)
\(= \dfrac{5}{4} . 0 = 0\)
