\[ 3. \left\{ \begin{array}{l} x^2 + 4y^2 - 2xy = 12 \\ 4y + xy + 12 = 4y^2 + 4x \end{array} \right. \]

----- Nội dung ảnh -----
\[
3. \left\{
\begin{array}{l}
x^2 + 4y^2 - 2xy = 12 \\
4y + xy + 12 = 4y^2 + 4x
\end{array}
\right.
\]