\(Bài1\\ a,=\dfrac{-3}{7}\left(\dfrac{4}{19}+\dfrac{15}{19}\right)+\dfrac{5}{7}\\ =\dfrac{-3}{7}.1+\dfrac{5}{7}\\ =-\dfrac{3}{7}+\dfrac{5}{7}\\ =\dfrac{2}{7}\\ b,=\dfrac{5}{9}\left(\dfrac{7}{13}+\dfrac{9}{113}-\dfrac{3}{13}\right)\\ =\dfrac{5}{9}.1=\dfrac{5}{9}\\ c,=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)+\dfrac{12}{19}\\ =\dfrac{7}{19}.1+\dfrac{12}{19}\\ =\dfrac{19}{19}=1\\ d,=\dfrac{6}{11}.\left(-\dfrac{2}{5}-\dfrac{3}{10}\right)\\ =\dfrac{6}{11}.-\dfrac{7}{10}\\ =-\dfrac{21}{55}\)
Đúng 3
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