You may have correctly used the Quadratic Formula, $\displaystyle{x}=\frac{{-{b}\pm\sqrt{{{{b}}^{{2}}-{4}{a}{c}}}}}{{{2}{a}}}\usepackage{cmbright}\Huge\$ , and substituted in $\displaystyle{a}={1},{b}={3}\usepackage{cmbright}\Huge\$ , and $\displaystyle{c}={1}\usepackage{cmbright}\Huge\$ . However, you thought that $\displaystyle\sqrt{{{9}-{4}}}\usepackage{cmbright}\Huge\$ simplified to $\displaystyle{3}-{2}={1}\usepackage{cmbright}\Huge\$ , but it is actually equal to $\displaystyle\sqrt{{5}}\usepackage{cmbright}\Huge\$ .