Câu 6:
a: \(\dfrac{-3}{14}+\dfrac{5}{8}-\dfrac{1}{2}\)
\(=\dfrac{-12+5\cdot7-28}{56}\)
\(=\dfrac{23-28}{56}=-\dfrac{5}{56}\)
b: \(\dfrac{5}{23}\cdot\left(\dfrac{13}{5}-\dfrac{14}{4}\right)\)
\(=\dfrac{5}{23}\cdot\dfrac{13\cdot4-14\cdot5}{20}\)
\(=\dfrac{5}{20}\cdot\dfrac{52-70}{23}=\dfrac{1}{4}\cdot\dfrac{-18}{23}=\dfrac{-9}{46}\)
Câu 5:
a: \(\left(-\dfrac{5}{24}+\dfrac{3}{4}+\dfrac{7}{12}\right):\dfrac{-15}{7}\)
\(=\dfrac{-5+18+14}{24}\cdot\dfrac{-7}{15}\)
\(=\dfrac{27}{24}\cdot\dfrac{-7}{15}\)
\(=\dfrac{9}{8}\cdot\dfrac{-7}{15}=\dfrac{9}{15}\cdot\dfrac{-7}{8}=\dfrac{-7}{8}\cdot\dfrac{3}{5}=\dfrac{-21}{40}\)
b: \(\left(\dfrac{2}{3}-\dfrac{11}{12}\right):2+\dfrac{17}{8}\)
\(=\dfrac{8-11}{12}:2+\dfrac{17}{8}\)
\(=\dfrac{-1}{4}:2+\dfrac{17}{8}=\dfrac{17}{8}-\dfrac{1}{8}=\dfrac{16}{8}=2\)
