smc

We are given $c=2$. So the product of the roots is $-c=-2$ by Vieta's formulas. These also tell us that $\frac{-a}{3}$ is the average of the zeros, so $\frac{-a}{3}=-2⟹a=6$. We are also given that the sum of the coefficients is $-2$, so $1+6+b+2=-2⟹b=-11$. So the answer is $\boxed{-11}$.