2: \(\dfrac{7}{12}-\dfrac{3}{4}\cdot\dfrac{5}{6}\)
\(=\dfrac{14}{24}-\dfrac{15}{24}=-\dfrac{1}{24}\)
3: \(1-\left(-\dfrac{5}{2}\right):\left(-\dfrac{3}{4}+\dfrac{2}{8}\right)\)
\(=1+\dfrac{5}{2}:\left(-\dfrac{3}{4}+\dfrac{1}{4}\right)\)
\(=1+\dfrac{5}{2}:\dfrac{-2}{4}\)
\(=1+\dfrac{5}{2}\cdot\dfrac{-4}{2}=1+\dfrac{-20}{4}=1-5=-4\)
4: \(\dfrac{4}{23}+\dfrac{5}{21}-\dfrac{4}{23}+0,5+\dfrac{16}{21}\)
\(=\left(\dfrac{4}{23}-\dfrac{4}{23}\right)+\left(\dfrac{5}{21}+\dfrac{16}{21}\right)+0,5\)
=0+1+0,5=1,5
5: \(\left(-0,8\right)+\dfrac{16}{3}\cdot\left(-\dfrac{5}{3}+\dfrac{7}{6}\right)^2\)
\(=-\dfrac{4}{5}+\dfrac{16}{3}\cdot\left(-\dfrac{10}{6}+\dfrac{7}{6}\right)^2\)
\(=-\dfrac{4}{5}+\dfrac{16}{3}\cdot\dfrac{1}{4}=-\dfrac{4}{5}+\dfrac{4}{3}=\dfrac{-12+20}{15}=\dfrac{8}{15}\)
6: \(25\cdot\left(-\dfrac{1}{5}\right)^3+\dfrac{1}{5}-2\cdot\left(-\dfrac{1}{2}\right)^2-\sqrt{\dfrac{1}{4}}\)
\(=25\cdot\dfrac{-1}{125}+\dfrac{1}{5}-2\cdot\dfrac{1}{4}-\dfrac{1}{2}\)
\(=-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{2}-\dfrac{1}{2}=-\dfrac{2}{2}=-1\)
8: \(\dfrac{7}{17}\cdot\dfrac{-5}{13}+\dfrac{7}{17}\cdot\dfrac{-8}{13}\)
\(=\dfrac{7}{17}\left(-\dfrac{5}{13}+\dfrac{-8}{13}\right)\)
\(=\dfrac{7}{17}\cdot\left(-1\right)=-\dfrac{7}{17}\)
9: \(\dfrac{4}{5}-\left[\left(-\dfrac{5}{2}\right)-\left(-\dfrac{3}{4}+\dfrac{2}{8}\right)\right]\)
\(=\dfrac{4}{5}-\left[-\dfrac{5}{2}+\dfrac{3}{4}-\dfrac{1}{4}\right]\)
\(=\dfrac{4}{5}-\left[-\dfrac{5}{2}+\dfrac{1}{2}\right]=\dfrac{4}{5}-\left(-2\right)=\dfrac{4}{5}+2=\dfrac{14}{5}\)
10: \(\left(-\dfrac{1}{3}\right)^2-\dfrac{3}{8}:\left(0,5\right)^3-\dfrac{5}{2}\cdot\left(-4\right)\)
\(=\dfrac{1}{9}-\dfrac{3}{8}:\dfrac{1}{8}+\dfrac{5}{2}\cdot4\)
\(=\dfrac{1}{9}-3+10\)
\(=\dfrac{1}{9}+7=\dfrac{64}{9}\)
11: \(\left[\left(\dfrac{1}{4}-0,5\right)\cdot2+\dfrac{8}{3}\right]:2\)
\(=\left[\left(\dfrac{1}{4}-\dfrac{1}{2}\right)\cdot2+\dfrac{8}{3}\right]:2\)
\(=\left(-\dfrac{1}{4}\cdot2+\dfrac{8}{3}\right):2\)
\(=\left(-\dfrac{2}{4}+\dfrac{8}{3}\right):2=-\dfrac{1}{4}+\dfrac{4}{3}=\dfrac{-3+16}{12}=\dfrac{13}{12}\)
\(8,\dfrac{7}{17}.\dfrac{-5}{13}+\dfrac{7}{17}.\dfrac{-8}{13}=\dfrac{7}{17}.\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)=\dfrac{7}{17}.\dfrac{-13}{13}=\dfrac{7}{17}.\left(-1\right)=\dfrac{-7}{17}\)
\(9,\dfrac{4}{5}-\left[\left(-\dfrac{5}{2}\right)-\left(\dfrac{-3}{4}+\dfrac{2}{8}\right)\right]\)
\(=\dfrac{4}{5}-\left[\dfrac{-5}{2}-\left(\dfrac{-6}{8}+\dfrac{2}{8}\right)\right]\)
\(=\dfrac{4}{5}-\left[\dfrac{-5}{2}-\dfrac{-4}{8}\right]\)
\(=\dfrac{4}{5}-\left[\dfrac{-20}{8}+\dfrac{4}{8}\right]\)
\(=\dfrac{4}{5}-\dfrac{-16}{8}\)
\(=\dfrac{4}{5}+2\)
\(=\dfrac{4}{5}+\dfrac{10}{5}\)
\(=\dfrac{14}{5}\)
\(10,\left(-\dfrac{1}{3}\right)^2-\dfrac{3}{8}:\left(0,5\right)^3-\dfrac{5}{2}.\left(-4\right)\)
\(=\dfrac{1}{9}-\dfrac{3}{8}:\dfrac{1}{8}-\left(-10\right)\)
\(=\dfrac{1}{9}-\dfrac{3}{8}.8+10\)
\(=\dfrac{1}{9}-3+10\)
\(=\dfrac{1}{9}-\dfrac{27}{9}+\dfrac{90}{9}\)
\(=\dfrac{64}{9}\)
\(11,\left[\left(\dfrac{1}{4}-0,5\right).2+\dfrac{8}{3}\right]:2\)
\(=\left[\left(\dfrac{1}{4}-\dfrac{1}{2}\right).2+\dfrac{8}{3}\right].\dfrac{1}{2}\)
\(=\left[\left(\dfrac{1}{4}-\dfrac{2}{4}\right).2+\dfrac{8}{3}\right].\dfrac{1}{2}\)
\(=\left[\dfrac{-1}{4}.2+\dfrac{8}{3}\right].\dfrac{1}{2}\)
\(=\left[\dfrac{-1}{2}+\dfrac{8}{3}\right].\dfrac{1}{2}\)
\(=\left[\dfrac{-3}{6}+\dfrac{16}{6}\right].\dfrac{1}{2}\)
\(=\dfrac{13}{6}.\dfrac{1}{2}\)
\(=\dfrac{13}{12}\)
\(2,\dfrac{7}{12}-\dfrac{3}{4}.\dfrac{5}{6}=\dfrac{7}{12}-\dfrac{5}{8}=\dfrac{14}{24}-\dfrac{15}{24}=\dfrac{-1}{24}\)
\(3,1-\left(-\dfrac{5}{2}\right):\left(\dfrac{-3}{4}+\dfrac{2}{8}\right)=1+\dfrac{5}{2}:\left(\dfrac{-6}{8}+\dfrac{2}{8}\right)=1+\dfrac{5}{2}:\dfrac{-4}{8}=1+\dfrac{5}{2}:\dfrac{-1}{2}=1+\dfrac{5}{2}.\left(-2\right)=1+\left(-5\right)=-4\)
\(4,\dfrac{4}{23}+\dfrac{5}{21}-\dfrac{4}{23}+0,5+\dfrac{16}{21}\)
\(=\left(\dfrac{4}{23}-\dfrac{4}{23}\right)+\left(\dfrac{5}{21}+\dfrac{16}{21}\right)+0,5\)
\(=0+\dfrac{21}{21}+\dfrac{1}{2}\)
\(=1+\dfrac{1}{2}=\dfrac{3}{2}\)
\(5,\left(-0,8\right)+\dfrac{16}{3}.\left(\dfrac{-5}{3}+\dfrac{7}{6}\right)^2\)
\(=\dfrac{-4}{5}+\dfrac{16}{3}.\left(\dfrac{-10}{6}+\dfrac{7}{6}\right)^2\)
\(=\dfrac{-4}{5}+\dfrac{16}{3}.\left(\dfrac{-3}{6}\right)^2\)
\(=\dfrac{-4}{5}+\dfrac{16}{3}.\left(\dfrac{-1}{2}\right)^2\)
\(=\dfrac{-4}{5}+\dfrac{16}{3}.\dfrac{1}{4}\)
\(=\dfrac{-4}{5}+\dfrac{4}{3}=\dfrac{-12}{15}+\dfrac{20}{15}=\dfrac{8}{15}\)
\(6)25.\left(\dfrac{-1}{5}\right)^3+\dfrac{1}{5}-2.\left(-\dfrac{1}{2}\right)^2-\sqrt{\dfrac{1}{4}}\)
\(=25.\dfrac{-1}{125}+\dfrac{1}{5}-2.\dfrac{1}{4}-\dfrac{1}{2}\)
\(=\dfrac{-1}{5}+\dfrac{1}{5}-\dfrac{1}{2}-\dfrac{1}{2}\)
\(=\left(\dfrac{-1}{5}+\dfrac{1}{5}\right)-\left(\dfrac{1}{2}+\dfrac{1}{2}\right)\)
\(=0-1\)
\(=-1\)
giải nhanh giúp mình vs ạ
