2- 1 phần 2 - 5 phần 2
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a: \(=\dfrac{5}{\dfrac{2}{5}}\cdot\dfrac{4}{\dfrac{2}{7}}+\dfrac{5}{\dfrac{5}{7}}\cdot\dfrac{5}{\dfrac{2}{5}}\)
\(=5\cdot\dfrac{5}{2}\cdot4\cdot\dfrac{7}{2}+5\cdot\dfrac{5}{2}\cdot5\cdot\dfrac{7}{5}\)
\(=\dfrac{25}{2}\left(14+7\right)=\dfrac{25}{2}\cdot21=\dfrac{525}{2}\)
b: \(=\dfrac{3}{4}-2+\dfrac{1}{2}\cdot\dfrac{12}{5}-\dfrac{1}{4}\)
\(=\dfrac{6}{5}-2+\dfrac{1}{2}=-\dfrac{3}{10}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài làm :
1)\(\frac{3}{2}+\frac{5}{2}-\frac{4}{2}=\frac{3+5-4}{2}=\frac{4}{2}=2\)
2)\(\frac{2}{5}\times\frac{1}{2}\div\frac{1}{3}=\frac{2\times1\times3}{5\times2\times1}=\frac{6}{10}=\frac{3}{5}\)
3)\(\frac{2}{9}\div\frac{9}{2}\times\frac{1}{2}=\frac{2\times2\times1}{9\times9\times2}=\frac{4}{162}=\frac{2}{81}\)
4)\(\left(\frac{4}{11}+\frac{3}{11}\right)\times\frac{2}{6}=\frac{4+3}{11}\times\frac{2}{6}=\frac{7}{11}\times\frac{2}{6}=\frac{7\times2}{11\times6}=\frac{14}{66}=\frac{7}{33}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{3}{2}\)\(+\)\(\frac{5}{2}\)\(-\)\(\frac{4}{2}\)\(=\)\(\left(\frac{3}{2}+\frac{5}{2}\right)-\frac{4}{2}\)
\(=\frac{8}{2}-\frac{4}{2}=\frac{4}{2}=2\)
\(\frac{2}{5}\)\(x\)\(\frac{1}{2}\)\(:\)\(\frac{1}{3}\)\(=\)\(\left(\frac{2}{5}x\frac{1}{2}\right)\)\(:\)\(\frac{1}{3}\)
\(=\)\(\frac{2}{10}\)\(:\)\(\frac{1}{3}\)\(=\frac{2}{10}x\frac{3}{1}\)\(=\frac{6}{10}=\frac{3}{5}\)
\(2-\frac{1}{2}-\frac{5}{2}\)
\(=\)\(\frac{2}{2}-\frac{5}{2}\)
\(=\)\(1-\frac{5}{2}\)
\(=\)\(\frac{-3}{2}\)