Incorrect. The domain of this expression excludes any values for a that will make the denominator of the expression equal to 0. In this case, factor $\displaystyle{{a}}^{{2}}-{4}\usepackage{cmbright}\Huge\$ into $\displaystyle{\left({a}+{2}\right)}{\left({a}-{2}\right)}\usepackage{cmbright}\Huge\$ . Which values for a will cause $\displaystyle{\left({a}+{1}\right)}{\left({a}+{2}\right)}{\left({a}-{2}\right)}\usepackage{cmbright}\Huge\$ to equal 0?