ĐKXĐ: ...
\(\left\{{}\begin{matrix}x+\frac{1}{x}+y+\frac{1}{y}=-4\\x\left(y+\frac{1}{y}\right)+\frac{1}{x}\left(y+\frac{1}{y}\right)=4\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x+\frac{1}{x}+y+\frac{1}{y}=-4\\\left(x+\frac{1}{x}\right)\left(y+\frac{1}{y}\right)=4\end{matrix}\right.\)
Theo Viet đảo, \(x+\frac{1}{x}\) và \(y+\frac{1}{y}\) là nghiệm của:
\(t^2+4t+4=0\Rightarrow t=-2\)
\(\Rightarrow\left[{}\begin{matrix}x+\frac{1}{x}=-2\\y+\frac{1}{y}=-2\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x^2+2x+1=0\\y^2+2y+1=0\end{matrix}\right.\)
\(\Leftrightarrow...\)
