Though $\displaystyle{2}\cdot{\left(-{14}\right)}=-{28}\usepackage{cmbright}\Huge\$ , $\displaystyle{2}+{\left(-{14}\right)}\ne-{3}\usepackage{cmbright}\Huge\$ . To factor $\displaystyle{{x}}^{{2}}-{3}{x}-{28}\usepackage{cmbright}\Huge\$ , you need to find integers r and s, whose product is $\displaystyle-{28}\usepackage{cmbright}\Huge\$ and whose sum is $\displaystyle-{3}\usepackage{cmbright}\Huge\$ . The correct answer is $\displaystyle{4}{x}-{7}{x}\usepackage{cmbright}\Huge\$ .