Correct. Recognizing that this expression is the product of a sum and a difference, you applied the pattern $\displaystyle{\left({a}+{b}\right)}{\left({a}-{b}\right)}={{a}}^{{2}}-{{b}}^{{2}}\usepackage{cmbright}\Huge\$ to come up wth the product $\displaystyle{64}{{x}}^{{4}}-{144}\usepackage{cmbright}\Huge\$ .