ĐKXĐ: x<>0; y<>0
\(\left\{{}\begin{matrix}\dfrac{2}{x}-\dfrac{1}{y^2}=-2\\\dfrac{1}{x}+\dfrac{2}{y^2}=9\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{2}{x}-\dfrac{1}{y^2}=-2\\\dfrac{2}{x}+\dfrac{4}{y^2}=18\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}\dfrac{2}{x}-\dfrac{1}{y^2}-\dfrac{2}{x}-\dfrac{4}{y^2}=-2-18\\\dfrac{1}{x}+\dfrac{2}{y^2}=9\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}-\dfrac{5}{y^2}=-20\\\dfrac{1}{x}=9-\dfrac{2}{y^2}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y^2=\dfrac{1}{4}\\\dfrac{1}{x}=9-2:\dfrac{1}{4}=9-8=1\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}y\in\left\{\dfrac{1}{2};-\dfrac{1}{2}\right\}\\x=1\end{matrix}\right.\left(nhận\right)\)
