\[y = 3x^{2} + bx + c;\ \ A( - 2;0);\]
\[x_{0} = - \frac{b}{2a}\]
\[b = - 2a \cdot x_{0} = - 2 \cdot 3 \cdot ( - 2) = 12;\]
\[3x^{2} + 12x + c = y\]
\[3 \cdot 4 + 12 \cdot ( - 2) + c = 0\]
\[12 - 24 + c = 0\]
\[c = 12.\]
\[Ответ:при\ b = 12;c = 12.\]