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a) \(1\frac{3}{19}+\frac{8}{21}-\frac{3}{19}+0.5+\frac{13}{21}\)
\(=\left(1\frac{3}{19}-\frac{3}{19}\right)+\left(\frac{8}{21}+\frac{13}{21}\right)+0.5\)
\(=1+1+0.5=2.5\)
b) \(\left(-\frac{3}{4}+\frac{2}{7}\right):\frac{3}{7}+\left(\frac{5}{7}+\frac{-1}{4}\right):\frac{3}{7}\)
\(=\left(\frac{-3}{4}+\frac{2}{7}+\frac{5}{7}+\frac{-1}{4}\right):\frac{3}{7}\)
\(=0:\frac{3}{7}=0\)
a)\(\frac{3}{7}\cdot19\frac{1}{3}-\frac{3}{7}\cdot33\frac{1}{3}\)
\(=\frac{3}{7}\cdot\left(19\frac{1}{3}-33\frac{1}{3}\right)\)
\(=\frac{3}{7}\cdot\left[\left(19-33\right)-\left(\frac{1}{3}-\frac{1}{3}\right)\right]\)
\(=\frac{3}{7}\cdot\left[\left(-14\right)-0\right]\)
\(=\frac{3}{7}\cdot\left(-14\right)=-6\)
b)\(9\cdot\left(-\frac{1}{3}\right)^3+\frac{1}{3}\)
\(=9\cdot\left(-\frac{1}{3}\right)^3-\left(-\frac{1}{3}\right)\)
\(=\left(-\frac{1}{3}\right)\cdot\left[9\cdot\left(-\frac{1}{3}\right)^2-1\right]\)
\(=\left(-\frac{1}{3}\right)\cdot\left[9\cdot\frac{1}{9}-1\right]\)
\(=\left(-\frac{1}{3}\right)\cdot\left[1-1\right]\)
\(=\left(-\frac{1}{3}\right)\cdot0=0\)
c)\(15\frac{1}{4}:\left(-\frac{5}{7}\right)-25\frac{1}{4}:\left(-\frac{5}{7}\right)\)
\(=\left(15\frac{1}{4}-25\frac{1}{4}\right):\left(-\frac{5}{7}\right)\)
\(=\left[\left(15-25\right)-\left(\frac{1}{4}-\frac{1}{4}\right)\right]\cdot\left(-\frac{7}{5}\right)\)
\(=\left[\left(-10\right)-0\right]\cdot\left(-\frac{7}{5}\right)\)
\(=\left(-10\right)\cdot\left(-\frac{7}{5}\right)=14\)
a.
\(\left(1\frac{1}{4}+\frac{3}{5}\right):\left(-\frac{11}{12}\right)+\left(\frac{3}{8}-1\frac{2}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\left(\frac{5}{4}+\frac{3}{5}+\frac{3}{8}-\frac{7}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\left(\frac{13}{8}-\frac{4}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\frac{33}{40}:\left(-\frac{11}{12}\right)\)
\(=\frac{33}{40}\cdot\left(-\frac{12}{11}\right)\)
\(=\frac{-9}{10}\)
b.
\(\left(\frac{3}{8}-1\frac{2}{5}\right):\left(-\frac{11}{15}\right)+\left(1\frac{1}{4}+\frac{3}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\left(\frac{3}{8}-\frac{7}{5}+\frac{5}{4}+\frac{3}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\left(\frac{13}{8}-\frac{4}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\frac{33}{40}:\left(-\frac{11}{15}\right)\)
\(=\frac{33}{40}\cdot\left(-\frac{15}{11}\right)\)
\(=\frac{-9}{8}\)
Thực hiện phép tính ( bằng cách hợp lí nếu có thể )
A. 2/3 - (- 1/4)+3/5-(+7/45)-(-5/9)+1/12+1/39
B. 6.(-2/3)^2 - 3(-2/3)^2 - 2 : (-3/2)+4
\(a,\dfrac{3}{5}+\dfrac{1}{5}.\dfrac{-17}{9}=\dfrac{3}{5}-\dfrac{17}{45}=\dfrac{27}{45}-\dfrac{17}{45}=\dfrac{10}{45}=\dfrac{2}{9}\\ b,\left(-\dfrac{4}{15}-\dfrac{18}{19}\right)-\left(\dfrac{20}{19}+\dfrac{11}{15}\right)=-\dfrac{4}{15}-\dfrac{18}{19}-\dfrac{20}{19}-\dfrac{11}{15}=\left(-\dfrac{4}{15}-\dfrac{11}{15}\right)-\left(\dfrac{18}{19}+\dfrac{20}{19}\right)=-1-2=-3\)
\(a,=\dfrac{3}{5}+\left(-\dfrac{17}{45}\right)=\dfrac{2}{9}\)
\(b,=-\dfrac{4}{15}-\dfrac{18}{19}-\dfrac{20}{19}-\dfrac{11}{15}=-3\)
`#3107.101107`
\(\dfrac{1}{4}+\dfrac{3}{4}\cdot19\dfrac{1}{3}-\dfrac{3}{4}\cdot39\dfrac{1}{3}\\ =\dfrac{1}{4}+\dfrac{3}{4}\cdot\left(19\dfrac{1}{3}-39\dfrac{1}{3}\right)\\ =\dfrac{1}{4}+\dfrac{3}{4}\cdot\left[\left(19-39\right)+\left(\dfrac{1}{3}-\dfrac{1}{3}\right)\right]\\ =\dfrac{1}{4}+\dfrac{3}{4}\cdot\left(-20\right)\\ =\dfrac{1}{4}+\left(-15\right)\\ =-\dfrac{59}{4}\)