Giải:
a) \(\dfrac{x}{5}=\dfrac{2}{x}\)
\(\Leftrightarrow x.x=2.5\)
\(\Leftrightarrow x^2=10\)
\(\Leftrightarrow x=\pm\sqrt{10}\)
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b) \(\dfrac{x}{y}=\dfrac{3}{5}\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=3\\y=5\end{matrix}\right.\)
Hoặc \(\left\{{}\begin{matrix}x=6\\y=10\end{matrix}\right.\)
Hoặc \(\left\{{}\begin{matrix}x=9\\y=15\end{matrix}\right.\)
v.v...
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