You may have thought that because $\displaystyle-{49}\usepackage{cmbright}\Huge\$ is the radicand, $\displaystyle-{7}\usepackage{cmbright}\Huge\$ would be the simplified expression. However, $\displaystyle-{7}\cdot-{7}={49}\usepackage{cmbright}\Huge\$ , not $\displaystyle-{49}\usepackage{cmbright}\Huge\$ . There is no real number value for the square root of a negative number.