Remember that the domain will exclude values for which the value of the denominator is 0. It looks like you tried to set the numerator equal to 0. When $\displaystyle{x}={1}\usepackage{cmbright}\Huge\$ , the value of the denominator is $\displaystyle{1}+{2}={3}\usepackage{cmbright}\Huge\$ , so $\displaystyle{x}={1}\usepackage{cmbright}\Huge\$ is within the domain of the expression. What is the value of x when $\displaystyle{x}+{2}={0}\usepackage{cmbright}\Huge\$ ?