Correct. Since 1296 = $\displaystyle{{36}}^{{2}}\usepackage{cmbright}\Huge\$ , the answer is 36. Alternatively, $\displaystyle{1296}={4}\cdot{324}={4}\cdot{4}\cdot{81}\usepackage{cmbright}\Huge\$ , so $\displaystyle\sqrt{{1296}}=\sqrt{{{{2}}^{{2}}\cdot{{2}}^{{2}}\cdot{{9}}^{{2}}}}={2}\cdot{2}\cdot{9}={36}\usepackage{cmbright}\Huge\$ .