\[- 12c^{3}\text{\ \ }\]
\[при\ \ \ c = - \frac{1}{2}:\]
\[- 12 \cdot \left( - \frac{1}{3} \right)^{3} = \frac{- 12}{- 8} = \frac{3}{2} = 1\frac{1}{2} = 1,5.\]