a: \(=\dfrac{-2}{5}\cdot\dfrac{4}{7}+\dfrac{-3}{5}\cdot\dfrac{9}{7}=\dfrac{-8-27}{35}=-1\)
b: \(=\dfrac{5}{9}\left(\dfrac{14}{17}+\dfrac{1}{17}+\dfrac{2}{17}\right)=\dfrac{5}{9}\)
c: \(=\dfrac{8}{11}\cdot\dfrac{5}{19}+\dfrac{7}{9}\cdot\dfrac{8}{11}-\dfrac{8}{11}\cdot\dfrac{1}{19}=\dfrac{8}{11}\left(\dfrac{4}{19}+\dfrac{7}{9}\right)=\dfrac{8}{11}\cdot\dfrac{169}{171}=\dfrac{1352}{1881}\)
\(a,\dfrac{-2}{5}\times\dfrac{4}{7}+\dfrac{-3}{5}\times\dfrac{2}{7}+\dfrac{-3}{5}\)
\(=\dfrac{-4}{5}\times\dfrac{2}{7}+\dfrac{2}{7}\times\dfrac{-3}{5}+\dfrac{-3}{5}\)
\(=\dfrac{2}{7}\left(\dfrac{-4}{5}+\dfrac{-3}{5}\right)-\dfrac{3}{5}\)
\(=\dfrac{-2}{5}-\dfrac{3}{5}=\dfrac{-5}{5}=-1\)
Câu còn lại tương tự nha
