bài 1
\(a,=-\dfrac{3}{7}\cdot\left(\dfrac{4}{19}+\dfrac{15}{19}\right)+\dfrac{5}{7}=-\dfrac{3}{7}\cdot1+\dfrac{5}{7}=-\dfrac{3}{7}+\dfrac{5}{7}=\dfrac{2}{7}\)
\(b.=\dfrac{5}{9}\cdot\left(\dfrac{7}{13}+\dfrac{9}{13}-\dfrac{3}{13}\right)=\dfrac{5}{9}\cdot1=\dfrac{5}{9}\)
\(c,=\dfrac{7}{19}\cdot\left(\dfrac{8}{11}+\dfrac{3}{11}\right)+\dfrac{12}{19}=\dfrac{7}{19}\cdot1+\dfrac{12}{19}=\dfrac{7}{19}+\dfrac{12}{19}=1\)
\(d,=\dfrac{6}{11}\cdot\dfrac{-2}{5}+\dfrac{6}{11}\cdot\dfrac{-3}{10}=\dfrac{6}{11}\cdot\left(\dfrac{-2}{5}+\dfrac{-3}{10}\right)=\dfrac{6}{11}\cdot\dfrac{-7}{10}-\dfrac{21}{55}\)
