Remember to apply the formula $\displaystyle{{\left({a}+{b}\right)}}^{{2}}={{a}}^{{2}}+{2}{a}{b}+{{b}}^{{2}}\usepackage{cmbright}\Huge\$ . What is $\displaystyle{{\left({15}{{x}}^{{2}}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ ?