\[2a^{2}b^{3} = - 3\]
\[a^{2}b^{3} = - \frac{3}{2}\]
\[2a^{4}b^{6} = 2 \cdot \left( a^{2}b^{3} \right)^{2} = 2 \cdot \left( - \frac{3}{2} \right)^{2} =\]
\[= 2 \cdot \frac{9}{4} = \frac{9}{2} = 4,5.\]