$\displaystyle{7}{x}{{y}}^{{5}}{\left({1}-{4}{{y}}^{{3}}\right)}={7}{x}{{y}}^{{5}}-{28}{x}{{y}}^{{8}}\ne{7}{{x}}^{{4}}{{y}}^{{5}}-{27}{x}{{y}}^{{8}}\usepackage{cmbright}\Huge\$ and $\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 neither of these equations is factored correctly.