Thực hiện phép tính:
a) \(\dfrac{-3}{5}\).\(\dfrac{2}{7}\)+\(\dfrac{-3}{7}\).\(\dfrac{3}{5}\)+\(\dfrac{-3}{7}\) b) ( -4\(\dfrac{2}{7}\).\(\dfrac{7}{11}\)+\(\dfrac{7}{11}\).5\(\dfrac{1}{3}\)).5-5\(\dfrac{2}{3}\)
c) \(\dfrac{5}{39}\).(7\(\dfrac{4}{5}\).1\(\dfrac{2}{3}\)+8\(\dfrac{1}{3}\).7\(\dfrac{4}{5}\))
a: \(\dfrac{-3}{5}\cdot\dfrac{2}{7}+\dfrac{-3}{7}\cdot\dfrac{3}{5}+\dfrac{-3}{7}\)
\(=\dfrac{-3}{7}\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\dfrac{-3}{7}\)
\(=-\dfrac{3}{7}+\dfrac{-3}{7}=-\dfrac{6}{7}\)
b: \(\left(-4\dfrac{2}{7}\cdot\dfrac{7}{11}+\dfrac{7}{11}\cdot5\dfrac{1}{3}\right)\cdot5-5\dfrac{2}{3}\)
\(=\dfrac{7}{11}\left(-4-\dfrac{2}{7}+5+\dfrac{1}{3}\right)\cdot5-\dfrac{17}{3}\)
\(=\dfrac{35}{11}\left(1-\dfrac{2}{7}+\dfrac{1}{3}\right)-\dfrac{17}{3}\)
\(=\dfrac{35}{11}\cdot\dfrac{21-6+7}{21}-\dfrac{17}{3}\)
\(=\dfrac{5}{3}\cdot\dfrac{22}{11}-\dfrac{17}{3}=\dfrac{10}{3}-\dfrac{17}{3}=\dfrac{-7}{3}\)
c: \(\dfrac{5}{39}\left(7\dfrac{4}{5}\cdot1\dfrac{2}{3}+8\dfrac{1}{3}\cdot7\dfrac{4}{5}\right)\)
\(=\dfrac{5}{39}\cdot7\dfrac{4}{5}\left(1+\dfrac{2}{3}+8+\dfrac{1}{3}\right)\)
\(=\dfrac{5}{39}\cdot\dfrac{39}{5}\cdot\left(9+1\right)=10\)
