Решебник по алгебре 7 класс Мерзляк ФГОС Задание 1264

\[\boxed{\text{1264.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[1)\ 2x - 3y = 8;\ \ 7x - 5y = - 5\]

\[\left\{ \begin{matrix} 2x - 3y = 8\ \ \ \ \ \ \ | \cdot 5\ \ \ \ \ \ \ \\ 7x - 5y = - 5\ \ \ \ | \cdot ( - 3) \\ \end{matrix} \right.\ \]

\[\left\{ \begin{matrix} 10x - 15y = 40\ \ \ \\ - 21x + 15y = 15 \\ \end{matrix} \right.\ ( + )\]

\[- 11x = 55\]

\[x = - 5;\]

\[3y = 2x + 8 = - 10 + 8 = - 2\]

\[y = - \frac{2}{3}.\]

\[Ответ:\left( - 5;\ - \frac{2}{3} \right).\]

\[2)\ 9x + y = 3;\ \ 8x + 3y = - 10\]

\[\left\{ \begin{matrix} 9x + y = 3\ \ \ | \cdot ( - 3) \\ 8x + 3y = - 10\ \ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \]

\[\left\{ \begin{matrix} - 27x - 3y = - 9 \\ 8x + 3y = - 10\ \ \ \\ \end{matrix} \right.\ \]

\[- 19x = - 19\]

\[x = 1;\]

\[y = 3 - 9x = 3 - 9 = - 6.\]

\[Ответ:(1;\ - 6).\]