Evaluate $\displaystyle{2}{{a}}^{{2}}-{3}{a}{b}+{{b}}^{{2}}-{4}{a}+{b}\usepackage{cmbright}\Huge\$ when $\displaystyle{a}=-{4}\usepackage{cmbright}\Huge\$ and $\displaystyle{b}=-{2}\usepackage{cmbright}\Huge\$ .