Though $\displaystyle{1}\cdot{22}={22}\usepackage{cmbright}\Huge\$ , $\displaystyle{1}+{22}\ne-{13}\usepackage{cmbright}\Huge\$ . To factor $\displaystyle{{x}}^{{2}}-{13}{x}+{22}\usepackage{cmbright}\Huge\$ , you need to find integers r and s, whose product is 22 and whose sum is $\displaystyle-{13}\usepackage{cmbright}\Huge\$ .