Incorrect. This expression is a perfect square trinomial because $\displaystyle{36}{{x}}^{{2}}={{\left({6}{x}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ , $\displaystyle{1}={{1}}^{{2}}\usepackage{cmbright}\Huge\$ , and $\displaystyle{12}{x}={2}\cdot{6}{x}\cdot{1}\usepackage{cmbright}\Huge\$ . This means that it is in the form $\displaystyle{{r}}^{{2}}+{2}{r}{s}+{{s}}^{{2}}\usepackage{cmbright}\Huge\$ , and so can be factored as $\displaystyle{{\left({r}+{s}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ . The correct answer is 6.