1. Tính :
a. \(\left(\dfrac{3}{4}:1\dfrac{1}{2}\right)-\left(\dfrac{5}{6}:\dfrac{1}{3}\right)\);
b. \(\left[\left(\dfrac{-1}{5}\right):\dfrac{1}{10}\right]-\dfrac{5}{7}.\left(\dfrac{2}{3}-\dfrac{1}{5}\right)\);
c. \(\left(-0.4\right)+2\dfrac{2}{5}.\left[\left(\dfrac{-2}{3}\right)+\dfrac{1}{2}\right]^2\).
a.
\(\left(\dfrac{3}{4}:\dfrac{3}{2}\right)-\left(\dfrac{5}{6}\times\dfrac{3}{1}\right)=\left(\dfrac{3}{4}\times\dfrac{2}{3}\right)-\dfrac{5}{2}\\ =\dfrac{2}{4}-\dfrac{5}{2}=\dfrac{1}{2}-\dfrac{5}{2}=-\dfrac{4}{2}=-2\)
b.
\(\left(\dfrac{-1}{5}\times\dfrac{10}{1}\right)-\dfrac{5}{7}\left(\dfrac{10}{15}-\dfrac{3}{15}\right)=-2-\dfrac{5}{7}\times\dfrac{7}{15}\\ =-2-\dfrac{1}{3}=-\dfrac{7}{3}\)
c.
\(\dfrac{-4}{10}+\dfrac{12}{5}\left(\dfrac{-4}{6}+\dfrac{3}{6}\right)^2=\dfrac{-2}{5}+\dfrac{12}{5}\times\dfrac{1}{36}=\dfrac{-2}{5}+\dfrac{1}{15}\\ =\dfrac{-6}{15}+\dfrac{1}{15}=\dfrac{-5}{15}=\dfrac{-1}{3}\)
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