Ta có
\(\left\{ \begin{array}{l}4x - 5y = 3\\3x - y = 16\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}4x - 5y = 3\\y = 3x - 16\end{array} \right. \\\Leftrightarrow \left\{ \begin{array}{l}y = 3x - 16\\4x - 5\left( {3x - 16} \right) = 3\end{array} \right.\Leftrightarrow \left\{ \begin{array}{l}y = 3x - 16\\4x - 15x + 80 = 3\end{array} \right.\)
\( \Leftrightarrow \left\{ \begin{array}{l}y = 3x - 16\\ - 11x = - 77\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}x = 7\\y = 3.7 - 16\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}x = 7\\y = 5\end{array} \right.\)
Vậy hệ phương trình có nghiệm duy nhất \((x;y)=(7;5)\)
