$\displaystyle{{x}}^{{4}}{{y}}^{{5}}{\left({7}-{27}{{y}}^{{3}}\right)}={7}{{x}}^{{4}}{{y}}^{{5}}-{27}{{x}}^{{4}}{{y}}^{{8}}\ne{7}{{x}}^{{4}}{{y}}^{{5}}-{27}{x}{{y}}^{{8}}\usepackage{cmbright}\Huge\$ , so this answer is incorrect.