Incorrect. $\displaystyle{{\left({a}-{b}\right)}}^{{2}}={{a}}^{{2}}-{2}{a}{b}+{{b}}^{{2}}\usepackage{cmbright}\Huge\$ . In this case, $\displaystyle{a}={2}{d}\usepackage{cmbright}\Huge\$ and $\displaystyle{b}={5}\usepackage{cmbright}\Huge\$ , so $\displaystyle{{\left({2}{d}-{5}\right)}}^{{2}}={{\left({2}{d}\right)}}^{{2}}-{2}{\left({2}{d}\right)}{\left({5}\right)}+{{5}}^{{2}}={4}{{d}}^{{2}}-{20}{d}+{25}\usepackage{cmbright}\Huge\$ . The correct answer is $\displaystyle{20}{d}\usepackage{cmbright}\Huge\$ .