Both $\displaystyle{40}{{x}}^{{5}}{y}-{24}{{x}}^{{8}}{{y}}^{{2}}={8}{{x}}^{{5}}{y}{\left({5}-{3}{{x}}^{{3}}{y}\right)}\usepackage{cmbright}\Huge\$ and $\displaystyle{40}{{x}}^{{5}}{y}-{24}{{x}}^{{8}}{{y}}^{{2}}={4}{{x}}^{{4}}{\left({10}{x}{y}-{6}{{x}}^{{4}}{{y}}^{{2}}\right)}\usepackage{cmbright}\Huge\$ are correct factorizations.