Đáp án:
\(\left\{ \begin{array}{l}
y = 5\\
x = 7
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
\left\{ \begin{array}{l}
xy + x + y + 1 = xy + 13\\
xy - x - 2y + 2 = xy - 15
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x + y = 12\\
- x - 2y = - 17
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y - 2y = 12 - 17\\
x + y = 12
\end{array} \right.\\
\to \left\{ \begin{array}{l}
- y = - 5\\
x + y = 12
\end{array} \right.
\end{array}\)
\( \to \left\{ \begin{array}{l}
y = 5\\
x = 7
\end{array} \right.\)
