Excluded values are the values of the variable that result in a denominator equal to 0. The excluded values here are the solutions to the equations $\displaystyle{{x}}^{{2}}-{16}={0}\usepackage{cmbright}\Huge\$ and $\displaystyle{x}-{4}={0}\usepackage{cmbright}\Huge\$ . The first equation can be rewritten as $\displaystyle{\left({x}+{4}\right)}{\left({x}-{4}\right)}={0}\usepackage{cmbright}\Huge\$ . The solutions are $\displaystyle{x}=-{4}\usepackage{cmbright}\Huge\$ and $\displaystyle{x}={4}\usepackage{cmbright}\Huge\$ .