\[\boxed{\text{497.}\text{\ }\text{ОК\ ГДЗ\ -\ домашка\ на\ 5}}\]
\[\textbf{а)}\ \left\{ \begin{matrix}
(x + y)(x - y) = 0 \\
2x - y = 1\ \ \ \ \ \ \ \ \ \ \ \ \ \ \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow 1)\left\{ \begin{matrix}
x + y = 0 \\
2x - y = 1 \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow \left\{ \begin{matrix}
x = - y\ \\
- 3y = 1 \\
\end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix}
y = - \frac{1}{3} \\
x = \frac{1}{3}\text{\ \ \ \ } \\
\end{matrix} \right.\ ,\]
\[2)\ \left\{ \begin{matrix}
x - y = 0\ \\
2x - y = 1 \\
\end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix}
x = y \\
y = 1 \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow \left\{ \begin{matrix}
x = 1 \\
y = 1 \\
\end{matrix}, \right.\ \]
\[\textbf{б)}\ \left\{ \begin{matrix}
x^{2} + y^{2} = 100\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\
(x - 7y)(x + 7y) = 0 \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow \left\{ \begin{matrix}
x = 7y \\
y² = 2\ \\
\end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix}
y = \pm \sqrt{2\ } \\
x = \pm 7\sqrt{2} \\
\end{matrix} \right.\ \]
\[2)\ \left\{ \begin{matrix}
x = - 7y\ \ \ \ \\
50y^{2} = 100 \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow \left\{ \begin{matrix}
y^{2} = 2\ \ \ \ \\
x = - 7y \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow \left\{ \begin{matrix}
y = \pm \sqrt{2\ } \\
x = \pm 7\sqrt{2.} \\
\end{matrix} \right.\ \]
\[\textbf{в)}\ \left\{ \begin{matrix}
x^{2} + y^{2} = 25\ \ \ \ \ \ \ \ \ \ \\
(x - 3)(y - 5) = 0 \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow 1)\left\{ \begin{matrix}
x = 3\ \ \\
y^{2} = 16 \\
\end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix}
x = 3\ \ \ \\
y = \pm 4 \\
\end{matrix} \right.\ ,\]
\[\ 2)\left\{ \begin{matrix}
y = 5 \\
x = 0. \\
\end{matrix} \right.\ \]
\[\textbf{г)}\ \left\{ \begin{matrix}
x^{2} - y^{2} = 50\ \\
x(y + 1) = 0 \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow 1)\left\{ \begin{matrix}
x = 0\ \ \ \ \ \ \\
y^{2} = - 50 \\
\end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow корней\ нет;\]
\[2)\ \left\{ \begin{matrix}
y = - 1 \\
x² = 51 \\
\end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix}
y = - 1\ \ \ \ \ \ \ \\
x = \pm \sqrt{51}. \\
\end{matrix} \right.\ \]
\[Ответ:а)\ \left( \frac{1}{3};\ - \frac{1}{3} \right);\ \ (1;1);\ \]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ б)\ \left( 7\sqrt{2};\sqrt{2} \right);\]
\[\text{\ \ }\left( - 7\sqrt{2};\sqrt{2} \right);\left( 7\sqrt{2};\ - \sqrt{2} \right);\]
\[\left( - 7\sqrt{2};\ - \sqrt{2} \right);\]
\(в)\ (0;5);\ \ (3;4);(3;\ - 4);\)
\(г)\ \left( \sqrt{51};\ - 1 \right);\left( \sqrt{51};1 \right).\)