\[y = ax^{2} + bx + c.\]
\[1)\ y(0) = - 3;\]
\[a \bullet 0^{2} + b \bullet 0 + c = - 3\]
\[c = - 3.\]
\[2)\ y(3) = 0;\]
\[a \bullet 3^{2} + b \bullet 3 - 3 = 0\]
\[9a + 3b - 3 = 0\]
\[3a + b - 1 = 0\]
\[b = 1 - 3a.\]
\[3)\ y( - 2) = 15;\]
\[a( - 2)^{2} + (1 - 3a)( - 2) - 3 = 15\]
\[4a - 2 + 6a - 3 = 15\]
\[10a = 20\]
\[a = 2;\]
\[b = 1 - 6 = - 5.\]
\[Ответ:\ \ a = 2;\ b = - 5;\ c = - 3.\]