Tìm các số thực x, y sao cho (x – 2y) + (x + y + 4)I = (2x + y) + 2yi

Ta có:

\(\left( {x - 2y} \right) + \left( {x + y + 4} \right)i = \left( {2x + y} \right) + 2yi\)

\(\begin{array}{l}
 \Leftrightarrow \left\{ {\begin{array}{*{20}{l}}
{x - 2y = 2x + y}\\
{x + y + 4 = 2y}
\end{array}} \right.\\
 \Leftrightarrow \left\{ {\begin{array}{*{20}{l}}
{x =  - 3y}\\
{x - y + 4 = 0}
\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}{l}}
{x =  - 3}\\
{y = 1}
\end{array}} \right.
\end{array}\)

Vậy \(x = -3, y = 1\).