Решите систему уравнений 7x-3y=-5; 3x+4y=-18.

Ответ:

\[\left\{ \begin{matrix} 7x - 3y = - 5\ \ \ \ | \cdot 4 \\ 3x + 4y = - 18\ \ | \cdot 3 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ }\]

\[\left\{ \begin{matrix} 28x - 12y = - 20 \\ 9x + 12y = - 54\ \ \ \\ \end{matrix} \right.\ ( + )\]

\[37x = - 74\]

\[x = - 2.\]

\[\left\{ \begin{matrix} x = - 2\ \ \ \ \ \ \ \ \ \\ 3y = 7x + 5 \\ \end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix} x = - 2\ \ \ \ \ \ \ \ \ \ \ \ \ \\ 3y = - 14 + 5 \\ \end{matrix} \right.\ \]

\[\left\{ \begin{matrix} x = - 2\ \ \ \\ 3y = - 9 \\ \end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix} x = - 2 \\ y = - 3 \\ \end{matrix} \right.\ \]

\[Ответ:( - 2; - 3).\]