a) Ta có: \(2-\left(\dfrac{3}{7}+\dfrac{1}{3}\right)-\left(2-\dfrac{4}{3}+\dfrac{2}{7}\right)+2-\left(4-\dfrac{5}{7}\right)\)
\(=2-\dfrac{3}{7}-\dfrac{1}{3}-2+\dfrac{4}{3}-\dfrac{2}{7}+2-4+\dfrac{5}{7}\)
\(=-2\)
b) Ta có: \(\dfrac{-3}{13}\cdot\left(\dfrac{44}{33}+\dfrac{4444}{3030}+\dfrac{444444}{404040}\right)\)
\(=\dfrac{-3}{13}\left(\dfrac{4}{3}+\dfrac{22}{15}+\dfrac{11}{10}\right)\)
\(=\dfrac{-3}{13}\cdot\left(\dfrac{40}{30}+\dfrac{44}{30}+\dfrac{33}{30}\right)\)
\(=\dfrac{-3}{13}\cdot\dfrac{117}{30}\)
\(=\dfrac{-9}{10}\)
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