You may have found the correct simplification, but then divided a number under the radical sign by a number not under the radical sign. Remember that $\displaystyle\frac{\sqrt{{a}}}{\sqrt{{b}}}=\sqrt{{\frac{{a}}{{b}}}}\usepackage{cmbright}\Huge\$ . This is not equal to $\displaystyle\frac{\sqrt{{a}}}{{b}}\usepackage{cmbright}\Huge\$ .