\[\left\{ \begin{matrix} x² + y² = 64 \\ y - x = a\ \ \ \ \ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ }\left\{ \begin{matrix} x² + y² = 64 \\ y = x + a\ \ \ \ \ \ \ \\ \end{matrix} \right.\ \]
\[Нет\ решений\ при\ a < - 8\sqrt{2}\text{\ \ }и\ \ \]
\[a > 8\sqrt{2}.\]