\[\boxed{\text{400\ (400).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ (x - 1)(y - 1) = 0\]
\[\textbf{б)}\ (x + 1)(y - x) = 0\]
\[\textbf{в)}\ (x - 1)(x + 2) = 0\]
\[\textbf{г)}\ (y + 1)(y - 2) = 0\]
\(\boxed{\text{400.}\text{\ }\text{ОК\ ГДЗ\ -\ домашка\ на\ 5}}\)
\[\left\{ \begin{matrix} x^{2} + y^{2} = 9\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ (x - 10)^{2} + y^{2} = 16 \\ \end{matrix} \right.\ \]
\[Нет\ решений.\]