2C
3C
4A
5B
6C
Tự luận:
1.a
\(\dfrac{-3}{7}+\dfrac{3}{7}:\left(-\dfrac{3}{2}\right)-\dfrac{1}{2}\)
\(=\dfrac{-3}{7}+\dfrac{3}{7}.\left(-\dfrac{2}{3}\right)-\dfrac{1}{2}\)
\(=\dfrac{-3}{7}+\dfrac{-2}{7}-\dfrac{1}{2}=\dfrac{-5}{7}-\dfrac{1}{2}\)
\(=\dfrac{-10}{14}-\dfrac{7}{14}=\dfrac{-17}{14}\)
b.
\(\dfrac{7}{6}:\dfrac{7}{3}+\left(\dfrac{1}{3}-\dfrac{1}{2}\right)^2.\left(\dfrac{1}{4}-\dfrac{5}{7}\right)\)
\(=\dfrac{7}{6}.\dfrac{3}{7}+\left(\dfrac{2}{6}-\dfrac{3}{6}\right)^2.\left(\dfrac{7}{28}-\dfrac{20}{28}\right)\)
\(=\dfrac{1}{2}+\left(-\dfrac{1}{6}\right)^2.\left(-\dfrac{13}{28}\right)\)
\(=\dfrac{1}{2}+\dfrac{1}{36}.\left(-\dfrac{13}{28}\right)\)
\(=\dfrac{1}{2}-\dfrac{13}{1008}\)
\(=\dfrac{504}{1008}-\dfrac{13}{1008}=\dfrac{491}{1008}\)
2.
a.
\(-\dfrac{2}{5}x+\dfrac{2}{3}=\dfrac{-3}{7}\)
\(-\dfrac{2}{5}x=\dfrac{-3}{7}-\dfrac{2}{3}\)
\(-\dfrac{2}{5}x=-\dfrac{23}{21}\)
\(x=\left(-\dfrac{23}{21}\right):\left(-\dfrac{2}{5}\right)\)
\(x=\dfrac{115}{42}\)
b.
\(\dfrac{1}{2}-\dfrac{2}{3}:\left(x-\dfrac{3}{5}\right)=\dfrac{-3}{4}\)
\(\dfrac{2}{3}:\left(x-\dfrac{3}{5}\right)=\dfrac{1}{2}-\dfrac{-3}{4}\)
\(\dfrac{2}{3}:\left(x-\dfrac{3}{5}\right)=\dfrac{5}{4}\)
\(x-\dfrac{3}{5}=\dfrac{2}{3}:\dfrac{5}{4}\)
\(x-\dfrac{3}{5}=\dfrac{8}{15}\)
\(x=\dfrac{8}{15}+\dfrac{3}{5}\)
\(x=\dfrac{17}{15}\)
