If the Rolle's theorem holds for the function $\mathrm{f}\left(\mathrm{x}\right)=2{\mathrm{x}}^3+{\mathrm{ax}}^2+\mathrm{bx}$ in the interval [-1, 1] for the point $\mathrm{c}=\frac{1}{2}$, then the value of $2\mathrm{a}+\mathrm{b}$ is