\[y = ax^{2} + bx - 3;\ \ \ A\ ( - 2;\ 7);\ \ \]
\[\text{B\ }(3;\ - 6)\]
\[\left\{ \begin{matrix} 4a - 2b - 3 = 7 \\ 9 + 3b - 3 = - 6 \\ \end{matrix}\text{\ \ \ \ \ \ } \right.\ \]
\[\left\{ \begin{matrix} 4a - 2b = 10\ \ \ \ \ |\ :2 \\ 9a + 3b = - 3\ \ \ \ \ |\ :3 \\ \end{matrix}\text{\ \ \ \ \ \ \ \ } \right.\ \]
\[\left\{ \begin{matrix} 2a - b = 5\ \ \\ 3a + b = - 1 \\ \end{matrix} \right.\ \ ( + )\]
\[\left\{ \begin{matrix} 5a = 4\ \ \ \ \ \ \ \ \ \ \ \ \\ b = - 1 - 3a \\ \end{matrix}\text{\ \ \ \ \ } \right.\ \]
\[\left\{ \begin{matrix} a = 0,8\ \ \ \\ b = - 3,4 \\ \end{matrix} \right.\ \]
\[Ответ:\ \ \ a = 0,8;\ \ \ \ \ \ b = - 3,4.\]