Correct. Since $\displaystyle{256}={{4}}^{{4}}\usepackage{cmbright}\Huge\$ , $\displaystyle{{256}}^{{-\frac{{3}}{{4}}}}={{\left({{256}}^{{\frac{{1}}{{4}}}}\right)}}^{{-{{3}}}}={{4}}^{{-{{3}}}}=\frac{{1}}{{{{4}}^{{3}}}}=\frac{{1}}{{64}}\usepackage{cmbright}\Huge\$ .