$\displaystyle-{243}=-{729}\div{3}\usepackage{cmbright}\Huge\$ , but it is not the cube root of -729. Find a number x so that $\displaystyle{{x}}^{{3}}=-{729}\usepackage{cmbright}\Huge\$ . Remember that $\displaystyle{{\left(-{1}\right)}}^{{3}}=-{1}\usepackage{cmbright}\Huge\$ .