Tính A=26:[3:(0,2-0,1) trên 2,5.(0,8+1,2) + (34,06-33,81).4 trên 6,84:(28,57-25,15)] + 2 trên 3 : 4 trên 21
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a)=\(\frac{1}{9}.\frac{2}{145}-\frac{13}{3}.\frac{2}{145}+\frac{2}{145}\)
=\(\frac{2}{145}\left(\frac{1}{9}-\frac{13}{3}+1\right)\)
=\(\frac{2}{145}.\frac{-29}{9}\)
=\(\frac{-2}{45}\)
Học tốt nha!!!^^
Đây là tính hợp lí ... mà câu a là 27,5 chứ không phải 2,75...
\(A=\dfrac{7,5-0,6+\dfrac{3}{7}+\dfrac{3}{13}}{27,5-2,2+\dfrac{11}{7}+\dfrac{11}{3}}=\dfrac{\dfrac{15}{2}-\dfrac{3}{5}+\dfrac{3}{7}+\dfrac{3}{13}}{\dfrac{55}{2}-\dfrac{11}{5}+\dfrac{11}{7}+\dfrac{11}{3}}\\ =\dfrac{3\left(\dfrac{5}{2}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{13}\right)}{11\left(\dfrac{5}{2}-\dfrac{1}{5}+\dfrac{1}{7}+\dfrac{1}{13}\right)}=\dfrac{3}{11}\)
b: \(=26:\left[\dfrac{3:0.1}{2.5\cdot2}+\dfrac{0.25\cdot4}{2}\right]+\dfrac{2}{3}\cdot\dfrac{21}{4}\)
\(=26:\left[\dfrac{30}{5}+1\right]+\dfrac{42}{12}\)
\(=\dfrac{26}{7}+\dfrac{42}{12}=\dfrac{101}{14}\)
c: \(=\left[\dfrac{4-3}{386}\cdot\dfrac{193}{17}+\dfrac{33}{34}\right]:\left[\dfrac{25}{4002}\cdot\dfrac{2001}{25}+\dfrac{9}{2}\right]\)
\(=\dfrac{\left(\dfrac{1}{34}+\dfrac{33}{34}\right)}{\dfrac{1}{2}+\dfrac{9}{2}}=1:5=\dfrac{1}{5}\)
Bài 1: Tìm x
a) Ta có: \(\dfrac{4}{3}:0.8=\dfrac{2}{3}:\left(0.1\cdot x\right)\)
\(\Leftrightarrow\dfrac{2}{3}:\left(\dfrac{1}{10}\cdot x\right)=\dfrac{4}{3}:\dfrac{4}{5}\)
\(\Leftrightarrow\dfrac{2}{3}:\left(\dfrac{1}{10}\cdot x\right)=\dfrac{4}{3}\cdot\dfrac{5}{4}=\dfrac{5}{3}\)
\(\Leftrightarrow x\cdot\dfrac{1}{10}=\dfrac{2}{3}:\dfrac{5}{3}=\dfrac{2}{3}\cdot\dfrac{3}{5}=\dfrac{2}{5}\)
\(\Leftrightarrow x=\dfrac{2}{5}:\dfrac{1}{10}=\dfrac{2}{5}\cdot10=\dfrac{20}{5}=4\)
Vậy: x=4
b) Ta có: \(\left|x\right|=-1.2\)
mà \(\left|x\right|\ge0\forall x\)
nên \(x\in\varnothing\)
Vậy: \(x\in\varnothing\)
Bài 2: Tính
a) Ta có: \(\left(-2.5\right)\cdot\left(-4\right)\cdot\left(-7.9\right)\)
\(=\left(2.5\cdot4\right)\cdot\left(-7.9\right)\)
\(=-7.9\cdot10=-79\)
b) Ta có: \(\left(-0.375\right)\cdot\dfrac{13}{3}\cdot\left(-2\right)^3\)
\(=\dfrac{3}{8}\cdot8\cdot\dfrac{13}{3}\)
\(=3\cdot\dfrac{13}{3}=13\)
\(\frac{0,8\times0,4\times1,25\times2,5\times31,8+68,2}{0,1\times12,5\times4\times2,5\times2\times8\times0,2\times5}\)
\(=\frac{\left(0,8\times1,25\right)\times\left(0,4\times2,5\right)\times31,8+68,2}{0,1\times\left(12,5\times8\right)\times\left(4\times2,5\right)\times2\times\left(0,2\times5\right)}\)
\(=\frac{1\times1\times31,8+68,2}{0,1\times100\times10\times2\times1}\)
\(=\frac{31,8+68,2}{0,1\times100\times10\times2\times1}=\frac{100}{200}=\frac{1}{2}\)
1000+26