Correct. $\displaystyle{{c}}^{{2}}-{7}{c}-{18}={\left({c}-{9}\right)}{\left({c}+{2}\right)}={0}\usepackage{cmbright}\Huge\$ , so $\displaystyle{c}={9}\usepackage{cmbright}\Huge\$ or $\displaystyle{c}=-{2}\usepackage{cmbright}\Huge\$ .