\[\boxed{\text{411\ (411).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ xy = 2;\ \ \ \ y = \frac{2}{x}\text{.\ }\]
\[(1;2);\ \ \ ( - 1;\ - 2);\ \ \ (2;1);\ \ \ \]
\[( - 2;\ - 1).\]
\[\textbf{б)}\ x^{2} - y^{2} = 3\]
\[(x - y)(x + y) = 3\]
\[x - y = \pm 1\]
\[x + y = \pm 3 \Longrightarrow \left\{ \begin{matrix} x = \pm 2 \\ y = \pm 1 \\ \end{matrix} \right.\ ;\]
\[(2;1);\ \ ( - 2;\ - 1);\ \ (2;\ - 1);\ \ \]
\[( - 2;1).\]