Correct. Rewrite in standard form by adding $\displaystyle{12}{x}\usepackage{cmbright}\Huge\$ to both sides: $\displaystyle{{x}}^{{2}}+{12}{x}+{36}={0}\usepackage{cmbright}\Huge\$

Use the Quadratic Formula, $\displaystyle{x}=\frac{{-{b}\pm\sqrt{{{{b}}^{{2}}-{4}{a}{c}}}}}{{{2}{a}}}\usepackage{cmbright}\Huge\$ , with $\displaystyle{a}={1},{b}={12}\usepackage{cmbright}\Huge\$ , and $\displaystyle{c}={36}\usepackage{cmbright}\Huge\$ :

$\displaystyle{x}=\frac{{-{12}\pm\sqrt{{{{12}}^{{2}}-{4}{\left({1}\right)}{\left({36}\right)}}}}}{{{2}\cdot{1}}}=\frac{{-{12}\pm\sqrt{{{144}-{144}}}}}{{2}}=\frac{{-{12}}}{{2}}=-{6}\usepackage{cmbright}\Huge\$