Решите систему уравнений:5x+8y=-1; x+2y=4.

\[\left\{ \begin{matrix}
5x + 8y = - 1\ \ \ \ \ \ \ \ \ \ \ \\
x + 2y = 4\ \ \ | \cdot ( - 4) \\
\end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ }\]

\[\left\{ \begin{matrix}
5x + 8y = - 1\ \ \ \ \ \ \ \ \ \ \ (1) \\
- 4x - 8y = - 16\ \ \ \ (2) \\
\end{matrix} \right.\ \]

\[x = - 17\]

\[\left\{ \begin{matrix}
x = - 17\ \ \ \ \ \\
x + 2y = 4 \\
\end{matrix} \right.\ \text{\ \ \ \ \ }\]

\[\left\{ \begin{matrix}
x = - 17\ \ \ \ \\
2y = 4 - x \\
\end{matrix} \right.\ \text{\ \ \ \ }\]

\[\left\{ \begin{matrix}
x = - 17\ \ \ \ \ \\
y = 2 - \frac{1}{2}x \\
\end{matrix} \right.\ \text{\ \ \ \ }\]

\[\left\{ \begin{matrix}
x = - 17\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\
y = 2 - \frac{1}{2} \cdot ( - 17) \\
\end{matrix} \right.\ \]

\[\left\{ \begin{matrix}
x = - 17\ \ \ \ \\
y = \frac{4}{2} + \frac{17}{2} \\
\end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ }\]

\[\left\{ \begin{matrix}
x = - 17 \\
y = \frac{21}{2}\text{\ \ \ } \\
\end{matrix} \right.\ \text{\ \ \ \ \ \ }\]

\[\left\{ \begin{matrix}
x = - 17 \\
y = 10,5 \\
\end{matrix} \right.\ \]

\[Ответ:( - 17;10,5).\]