Bài 1:
a) \(\dfrac{-4}{7}+\left(\dfrac{-2}{3}+\dfrac{4}{7}\right)=\dfrac{-4}{7}-\dfrac{2}{3}+\dfrac{4}{7}=\dfrac{-2}{3}\)
c) \(\left(\dfrac{4}{5}+\dfrac{2}{3}\right):\dfrac{1}{5}-1\dfrac{2}{5}.\left(\dfrac{-5}{7}\right)^2=\left(\dfrac{12}{15}+\dfrac{10}{15}\right).5-\dfrac{7}{5}.\dfrac{25}{49}=\dfrac{22}{15}.5-\dfrac{1}{1}.\dfrac{5}{7}=\dfrac{22}{3}.1-\dfrac{5}{7}=\dfrac{33}{2}-\dfrac{5}{7}=\dfrac{221}{14}\)
b)\(\dfrac{-3}{7}.\dfrac{5}{9}+\dfrac{4}{9}.\dfrac{-3}{7}+2\dfrac{3}{7}=\dfrac{-3}{7}.\dfrac{5}{9}+\dfrac{4}{9}.\dfrac{-3}{7}+\dfrac{17}{7}=\dfrac{-3}{7}.\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\dfrac{17}{7}=\dfrac{-3}{7}.1+\dfrac{17}{9}=\dfrac{-3}{7}+\dfrac{17}{7}=\dfrac{14}{7}=2\)
