- Với \(y=0\) ko phải nghiệm
- Với \(y\ne0\) hệ tương đương:
\(\left\{{}\begin{matrix}\dfrac{x^2+1}{y}-\left(x+y\right)=0\\\left(\dfrac{x^2+1}{y}\right)\left(x+y-2\right)+1=0\end{matrix}\right.\)
Đặt \(\left\{{}\begin{matrix}\dfrac{x^2+1}{y}=u\\x+y=v\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}u-v=0\\u\left(v-2\right)+1=0\end{matrix}\right.\)
\(\Rightarrow u\left(u-2\right)+1=0\Leftrightarrow u=1\)
\(\Rightarrow\left\{{}\begin{matrix}\dfrac{x^2+1}{y}=1\\x+y=1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x^2+1=y\\x+y=1\end{matrix}\right.\)
\(\Rightarrow x^2+x=0\Rightarrow...\)