Решите систему уравнений 7x+6y=29; 3x-5y=20.

Ответ:

\[\left\{ \begin{matrix} 7x + 6y = 29\ \ | \cdot 5 \\ 3x - 5y = 20\ \ | \cdot 6 \\ \end{matrix} \right.\ \]

\[\left\{ \begin{matrix} 35x + 30y = 145 \\ 18x - 30y = 120 \\ \end{matrix} \right.\ \text{\ \ }( + )\]

\[53x = 265\]

\[x = 5.\]

\[\left\{ \begin{matrix} x = 5\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ 5y = 3x - 20 \\ \end{matrix} \right.\ \]

\[5y = 3 \cdot 5 - 20\]

\[5y = - 5\]

\[y = - 1.\]

\[\left\{ \begin{matrix} x = 5\ \ \ \\ y = - 1 \\ \end{matrix} \right.\ \]

\[Ответ:(5; - 1).\]