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a/ \(\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-\frac{32}{17}+\frac{14}{21}=\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{7}{21}+\frac{14}{21}\right)-\frac{32}{17}=1+1-\frac{32}{17}=\frac{2}{17}\)
\(\left(3-\frac{1}{4}+\frac{2}{3}\right)-\left(5-\frac{1}{3}-\frac{6}{5}\right)-\left(6-\frac{7}{4}+\frac{3}{2}\right)\)
\(=3-\frac{1}{4}+\frac{2}{3}-5+\frac{1}{3}+\frac{6}{5}-6+\frac{7}{4}-\frac{3}{2}\)
\(=\left(3-5-6\right)+\left(\frac{-1}{4}+\frac{7}{4}-\frac{3}{2}\right)+\left(\frac{2}{3}+\frac{1}{3}\right)+\frac{6}{5}\)
\(=-8+\left(\frac{3}{2}-\frac{3}{2}\right)+1+\frac{6}{5}\)
\(=-7+\frac{6}{5}\)
\(=\frac{-35}{5}+\frac{6}{5}=-\frac{29}{5}\)
\(\left(-2\right)^3.\left(\frac{3}{4}-0,25\right):\left(2\frac{1}{4}-1\frac{1}{6}\right)\)
\(=-8.\left(\frac{3}{4}-\frac{1}{4}\right):\left(\frac{9}{4}-\frac{7}{6}\right)\)
\(=-8.\frac{1}{2}:\left(\frac{54}{24}-\frac{28}{24}\right)\)
\(=-4:\frac{13}{12}\)
\(=-4.\frac{13}{12}\)
\(=\frac{-13}{3}\)
\((-2)^3\cdot(\frac{3}{4}-0,25):(2\frac{1}{4}-1\frac{1}{6})\)
\(=-8\cdot(0,75-0,25):(\frac{9}{4}-\frac{7}{6})\)
\(=-8\cdot0,5:\frac{13}{12}\)
\(=-8\cdot0,5\cdot\frac{12}{13}\)
\(=-4\cdot\frac{12}{13}=-\frac{48}{13}=-3\frac{9}{13}\)
\(=2\frac{4}{13}\)
\(\text{Bài toán này .... tính mất công }:)\text{ Bạn dùng máy tính thử kiểm tra có đúng không ?}\)
\(\left(-2\right)^3.\left(\frac{3}{4}-0,25\right):\left(2\frac{1}{4}-1\frac{1}{6}\right)\)
\(=\left(-8\right).\left(\frac{3}{4}-\frac{1}{4}\right):\left(\frac{9}{4}-\frac{7}{6}\right)\)
\(=\left(-8\right).\frac{1}{2}:\frac{13}{12}\)
\(=\left(-4\right).\frac{12}{13}\)
\(=\frac{-48}{13}\)