tính nhanh
\(0,8\cdot2\frac{2}{3}\cdot10\cdot0,375\cdot\left(\frac{-5}{8}\right)\)
K
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18 tháng 11 2017
A) \(=\frac{\left(-1\right).2^{17}.5^6.3^{12}}{2^{16}.5^53^{13}}=\frac{10}{3}\)
B) Tương tự câu A bạn tự làm nha
26 tháng 6 2019
\(\left(1\cdot2\right)^{-1}+\left(2\cdot3\right)^{-1}+\cdot\cdot\cdot+\left(9\cdot10\right)^{-1}\)
\(=\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\cdot\cdot\cdot+\frac{1}{9\cdot10}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\cdot\cdot\cdot+\frac{1}{9}-\frac{1}{10}\)
\(=1-\frac{1}{10}\)
\(=\frac{9}{10}\)
26 tháng 6 2019
\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\cdot\cdot\cdot+\frac{1}{9\cdot10}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\cdot\cdot\cdot+\frac{1}{9}-\frac{1}{10}\)
\(=1-\frac{1}{10}\)
\(=\frac{9}{10}\)
28 tháng 4 2018
\(A=4+\left(1-\frac{1}{2}\right)\cdot\left(1-\frac{1}{3}\right)\cdot\left(1-\frac{1}{4}\right)\cdot...\cdot\left(1-\frac{1}{19}\right)\cdot\left(1-\frac{1}{20}\right)\)
\(A=4+\left(\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot...\cdot\frac{18}{19}\cdot\frac{19}{20}\right)\)
\(A=4+\frac{1\cdot2\cdot3\cdot...\cdot18\cdot19}{2\cdot3\cdot4\cdot...\cdot19\cdot20}\)
\(A=4+\frac{1}{20}\)
\(A=\frac{81}{20}\)
12 tháng 6 2018
\(\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{8.9.10}\right).x=\frac{23}{45}\)
\(\frac{1}{2}.\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+...+\frac{2}{8.9.10}\right).x=\frac{23}{45}\)
\(\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{8.9}-\frac{1}{9.10}\right).x=\frac{23}{45}\)
\(\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{9.10}\right).x=\frac{23}{45}\)
\(\frac{1}{2}.\frac{22}{45}.x=\frac{23}{45}\)
\(\frac{11}{45}.x=\frac{23}{45}\)
\(x=\frac{23}{45}:\frac{11}{45}\)
\(x=\frac{23}{11}\)
A
21 tháng 6 2019
\(\left(\sqrt{\frac{1}{4}\cdot\frac{1}{2}}-\frac{3}{2}\sqrt{2}+\frac{4}{5}\cdot10\sqrt{2}\right):\frac{1}{8}\)
\(=\left(\sqrt{\frac{1}{4}\cdot\frac{1\cdot2}{2\cdot2}}-\frac{3}{2}\sqrt{2}+\frac{4}{5}\cdot10\sqrt{2}\right):\frac{1}{8}\)
\(=\left(\sqrt{\frac{1}{4}\cdot\frac{2}{4}}-\frac{3}{2}\sqrt{2}+8\sqrt{2}\right):\frac{1}{8}\)
\(=\left(\sqrt{\frac{2}{16}}-\frac{3}{2}\sqrt{2}+8\sqrt{2}\right):\frac{1}{8}\)
\(=\left(\frac{1}{4}\sqrt{2}-\frac{3}{2}\sqrt{2}+8\sqrt{2}\right):\frac{1}{8}\)
\(=\sqrt{2}\left(\frac{1}{4}-\frac{3}{2}+8\right):\frac{1}{8}\)
\(=\sqrt{2}\left(\frac{1}{4}-\frac{6}{4}+\frac{32}{4}\right):\frac{1}{8}\)
\(=\sqrt{2}\cdot\frac{27}{4}:\frac{1}{8}\)
\(=\frac{27\sqrt{2}}{4}\cdot\frac{8}{1}\)
\(=2\cdot27\sqrt{2}=54\sqrt{2}\)
\(\Rightarrow\left(\sqrt{\frac{1}{4}\cdot\frac{1}{2}}-\frac{3}{2}\sqrt{2}+\frac{4}{5}\cdot10\sqrt{2}\right):\frac{1}{8}=54\sqrt{2}\)
21 tháng 6 2019
\(\left(\frac{1}{4}\sqrt{2}-\frac{3}{2}\sqrt{2}+\frac{4}{5}.10\sqrt{2}\right):\frac{1}{8}\)
=\(\sqrt{2}\)(1/4-3/2+8):1/8
=\(\sqrt{2}\).27/4.8
=54\(\sqrt{2}\)
\(0,8\cdot2\frac{2}{3}\cdot10\cdot0,375\cdot\left(\frac{-5}{8}\right)\)
\(=\frac{4}{5}\cdot\frac{8}{3}\cdot10\cdot\frac{3}{8}\cdot\left(\frac{-5}{8}\right)\)
\(=\left(\frac{8}{3}\cdot\frac{3}{8}\right)\cdot\left(\frac{4}{5}\cdot10\right)\cdot\left(\frac{-5}{8}\right)\)
\(=1\cdot8\cdot\left(\frac{-5}{8}\right)\)
\(=8\cdot\left(\frac{-5}{8}\right)\)
\(=-5\)
~Học tốt~