\[\left\{ \begin{matrix} x^{2} + y^{2} = 25 \\ y - 2x = 0\ \ \ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ }\left\{ \begin{matrix} x^{2} + y^{2} = 5^{2} \\ y = 2x\ \ \ \ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \]
\[( - 2,2;\ - 4,\ 4);\ \ (2,2;4,4).\]