You may have calculated $\displaystyle-\frac{{1}}{{2}}{{\left({4}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ by multiplying $\displaystyle-\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ times 4 first. You need to evaluate exponents before multiplication. The correct answer is $\displaystyle-{5}\usepackage{cmbright}\Huge\$ .