You may have rewritten the equation as $\displaystyle{4}{{x}}^{{2}}+{1}-{10}{x}={0}\usepackage{cmbright}\Huge\$ , instead of in standard form, and then substituted in the wrong values for b and c. You should be using $\displaystyle{a}={4},{b}=-{10}\usepackage{cmbright}\Huge\$ , and $\displaystyle{c}={1}\usepackage{cmbright}\Huge\$ in the formula: $\displaystyle{x}=\frac{{-{b}\pm\sqrt{{{{b}}^{{2}}-{4}{a}{c}}}}}{{{2}{a}}}\usepackage{cmbright}\Huge\$