Đáp án:
a) `A = 34/37`
b) `B = (-346)/13`
Giải thích các bước giải:
a) $A=-2\dfrac{3}{7}:\bigg(-12\dfrac{1}{2}+15\dfrac{1}{7}\bigg).\bigg(-3\dfrac{3}{10}\bigg)-\bigg(-\dfrac{34}{37}\bigg).\bigg(2\dfrac{1}{10}-4\dfrac{2}{5}\bigg)\\=\dfrac{-17}{7}:\dfrac{37}{14}.\bigg(-3\dfrac{3}{10}\bigg)-\bigg(-\dfrac{34}{37}\bigg).\dfrac{-23}{10}\\= \dfrac{-17}{7}.\dfrac{14}{37}.\dfrac{-33}{10}-\dfrac{391}{185}\\= \dfrac{561}{185}-\dfrac{391}{185}=\dfrac{34}{37}$
b) $B=-3\dfrac{1}{10}:\bigg(\dfrac{1}{2}-\dfrac{2}{5}\bigg)-2\dfrac{1}{28}:\bigg(\dfrac{2}{7}-\dfrac{3}{4}\bigg)\\= \dfrac{-31}{10}:\dfrac{1}{10}-\dfrac{57}{28}:\dfrac{-13}{28}\\= \dfrac{-31}{10}.10-\dfrac{57}{28}.\dfrac{-28}{13}\\= -31-\dfrac{-57}{13}=\dfrac{-346}{13}$
