$\begin{array}{l}
I\left\{ \begin{array}{l}
{x^2} - 2xy + x + y = 0\\
{x^4} - 4{x^2}y + 3{x^2} + {y^2} = 0
\end{array} \right.\\
D = R\\
TH1:x = 0 \to y = 0\\
TH2:x \ne 0\\
I \leftrightarrow \left\{ \begin{array}{l}
x - 2y + 1 + \frac{y}{x} = 0\;(chia\;ca\;hai\;ve\;cho\;x)\\
{x^2} - 4y + 3 + \frac{{{y^2}}}{{{x^2}}} = 0\;(chia\;ca\;hai\;ve\;cho\;{x^2})
\end{array} \right.\\
dat\left\{ \begin{array}{l}
a = x + \frac{y}{x}\\
b = y
\end{array} \right. \to {a^2} = {x^2} + \frac{{{y^2}}}{{{x^2}}} + 2b\\
\to I\;tro\;thanh:\left\{ \begin{array}{l}
a - 2b + 1 = 0\\
{a^2} - 2b - 4b + 3 = 0
\end{array} \right.\\
\leftrightarrow ...
\end{array}$