\[a = \frac{1}{2};\ \ b = - 1:\]
\[- 3,2a^{2}b^{3} =\]
\[= - 3,2 \cdot \left( \frac{1}{2} \right)^{2} \cdot ( - 1)^{3} =\]
\[= - 3,2 \cdot \frac{1}{4} \cdot ( - 1) = 0,8.\ \]