jmc

We have $a=1\frac{1}{2}=\frac{3}{2}$. When $a=\frac{3}{2}$, we find $2a-3=2\cdot \frac{3}{2}-3=3-3=0$, so the given expression equals $5a^2-13a+4$ times 0, which is $\boxed{0}$.