Tìm x € Q biết: [x+(2/5)]5=[x+(2/5)]3
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\(\left(\frac{2}{3}x-\frac{1}{5}\right).\left(\frac{3}{5}x+\frac{2}{3}\right)< 0\)
\(TH1:\frac{2}{3}x-\frac{1}{5}< 0\)
\(\frac{2}{3}x< \frac{1}{5}\)
\(x< \frac{1}{5}:\frac{2}{3}\)
\(x< \frac{3}{10}\)
\(TH2:\frac{3}{5}x+\frac{2}{3}< 0\)
\(\frac{3}{5}x< \frac{-2}{3}\)
\(x< \frac{-2}{3}:\frac{3}{5}\)
\(x< \frac{-10}{9}\)
vậy ....
hc tốt
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2x\left(x-3\right)+5\left(x-3\right)=0\)
\(\Leftrightarrow\left(2x+5\right)\left(x-3\right)=0\)\(\Leftrightarrow\orbr{\begin{cases}2x+5=0\\x-3=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{-5}{2}\\x=3\end{cases}}\)
Chọn ( B )
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a, \(3x-5=13\Leftrightarrow3x=18\Leftrightarrow x=6\)
b, \(4x-2=3x+1\Leftrightarrow x=3\)
c, \(5\left(x-3\right)-2\left(x-5\right)=58\Leftrightarrow5x-15-2x+10=58\)
\(\Leftrightarrow3x-5=58\Leftrightarrow3x=63\Leftrightarrow x=21\)
d, \(mx+5x=m^2m^2-25\Leftrightarrow x\left(m+5\right)=m^4-25\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(2\frac{1}{2}-\left(q-\frac{1}{2}\right)=\frac{3}{5}\)
\(\Rightarrow q-\frac{1}{2}=2\frac{1}{2}-\frac{3}{5}=\frac{19}{10}\)
\(\Rightarrow q=\frac{19}{10}+\frac{1}{2}=\frac{12}{5}=2,4\)
\(\Rightarrow q=2,4\)
b) \(\frac{1}{3}\cdot q-\frac{1}{5}\cdot q=0,6\)
\(=q\cdot\left(\frac{1}{3}-\frac{1}{5}\right)=0,6\)
\(=q\cdot\frac{2}{15}=0,6\)
\(\Rightarrow q=0,6:\frac{2}{15}=\frac{9}{2}=4,5\)
\(\Rightarrow q=4,5\)
c) \(\frac{3}{5}-q:\frac{1}{2}=\frac{1}{7}\)
\(\Rightarrow q:\frac{1}{2}=\frac{3}{5}-\frac{1}{7}=\frac{16}{35}\)
\(\Rightarrow q=\frac{16}{35}\cdot\frac{1}{2}=\frac{8}{35}\)
\(\Rightarrow q=\frac{5}{35}\)
Ở câu b áp dụng phân phối giữa phép nhân vs phép trừ.
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{1}{3}x+\frac{2}{5}\left(x-1\right)=0\)
\(\Leftrightarrow\frac{1}{3}x+\frac{2}{5}x-\frac{2}{5}=0\)
\(\Leftrightarrow\frac{11}{15}x=\frac{2}{5}\)
\(\Leftrightarrow x=\frac{2}{5}\div\frac{11}{15}=\frac{2.15}{5.11}=\frac{6}{11}\)
Vậy x = 6/11
a) \(\frac{1}{3}.x+\frac{2}{5}.\left(x-1\right)=0\)
\(\frac{1}{3}.x+\frac{2}{5}.x-\frac{2}{5}=0\)
\(x.\left(\frac{1}{3}+\frac{2}{5}\right)-\frac{2}{5}=0\)
\(x.\frac{11}{15}-\frac{2}{5}=0\)
\(x.\frac{11}{15}=\frac{2}{5}\)
\(x=\frac{2}{5}:\frac{11}{15}\)
\(x=\frac{6}{11}\)
b) \(3.\left(x-\frac{1}{2}\right)-5.\left(x+\frac{3}{5}\right)=x+\frac{1}{5}\)
\(3x-\frac{3}{2}-5x-3=x+\frac{1}{5}\)
\(3x-5x-\left(\frac{3}{2}+3\right)=x+\frac{1}{5}\)
\(-2x-\frac{9}{2}=x+\frac{1}{5}\)
\(\Rightarrow-2x-x=\frac{1}{5}+\frac{9}{2}\)
\(-3x=\frac{47}{10}\)
\(x=\frac{47}{10}:\left(-3\right)\)
\(x=\frac{-47}{30}\)
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