\[y = \frac{8}{\sqrt{12 + x - x^{2}}}\]
\[12 + x - x^{2} > 0\]
\[x_{1} + x_{2} = 1,\ \ x_{1} = 4\]
\[x_{1} \cdot x_{2} = - 12,\ \ x_{2} = - 3\]
\[D(y) = ( - 3;4).\]