Dùng phương pháp thế để giải hệ phương trình sau: \(\left\{ \begin{array}{l}4x - y = 2\\x + 3y = 7\end{array} \right.\)
\(\begin{array}{l}\left\{ \begin{array}{l}4x - y = 2\\x + 3y = 7\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}y = 4x - 2\\x + 3\left( {4x - 2} \right) = 7\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}y = 4x - 2\\x + 12x - 6 = 7\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}y = 4x - 2\\13x = 13\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}x = 1\\y = 2\end{array} \right.\end{array}\)