\[\boxed{\text{500\ (500).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ \left\{ \begin{matrix} y \geq x^{2} \\ y \leq 4\ \ \\ \end{matrix} \right.\ \]
\[\textbf{б)}\ \left\{ \begin{matrix} x^{2} + y^{2} \leq 4 \\ x - y \geq 0\ \ \ \ \ \\ \end{matrix} \right.\ \]
\[\textbf{в)}\ \left\{ \begin{matrix} x^{2} + y^{2} \leq 9\ \ \ \ \ \ \ \ \ \ \ \\ (x - 3)^{2} + y^{2} \leq 9 \\ \end{matrix} \right.\ \]
\[\textbf{г)}\ \left\{ \begin{matrix} (x - 2)^{2} + (y + 1)^{2} \geq 1 \\ (x - 2)^{2} + (y + 1)^{2} \leq 9 \\ \end{matrix} \right.\ \ \]