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Câu 2:
\(\dfrac{7}{9}\cdot\dfrac{3}{35}=\dfrac{1}{5}\cdot\dfrac{1}{3}=\dfrac{1}{15}\)
\(\dfrac{9}{22}\cdot55=\dfrac{9\cdot55}{22}=\dfrac{9\cdot5}{2}=\dfrac{45}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Trả lời:
\(194-24\div\left(44x-3\right)-25=145\)
\(\Leftrightarrow194-24\div\left(44x-3\right)=170\)
\(\Leftrightarrow24\div\left(44x-3\right)=24\)
\(\Leftrightarrow44x-3=1\)
\(\Leftrightarrow44x=4\)
\(\Leftrightarrow x=\frac{1}{11}\)
Vậy \(x=\frac{1}{11}\)
\(x\times\frac{1}{3}\div\frac{2}{9}-x\div5=1\frac{2}{5}\)
\(\Leftrightarrow x\times\frac{1}{3}\times\frac{9}{2}-x\times\frac{1}{5}=\frac{7}{5}\)
\(\Leftrightarrow x\times\frac{3}{2}-x\times\frac{1}{5}=\frac{7}{5}\)
\(\Leftrightarrow x\times\left(\frac{3}{2}-\frac{1}{5}\right)=\frac{7}{5}\)
\(\Leftrightarrow x\times\frac{13}{10}=\frac{7}{5}\)
\(\Leftrightarrow x=\frac{14}{13}\)
Vậy \(x=\frac{14}{13}\)
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3/1x4 + 3/4x7 +...+ 3/169x172
=(1/1 - 1/4 + 1/4 - 1/7 +...+ 1/169 - 1/172)
=1/1 - 1/172
=171/172
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