First, you can factor out a common factor of 5. Then, a binomial in the form $\displaystyle{{a}}^{{3}}+{{b}}^{{3}}\usepackage{cmbright}\Huge\$ can be factored as $\displaystyle{\left({a}+{b}\right)}{\left({{a}}^{{2}}-{a}{b}+{{b}}^{{2}}\right)}\usepackage{cmbright}\Huge\$ .

$\displaystyle{40}+{5}{{d}}^{{3}}={5}{\left({8}+{{d}}^{{3}}\right)}={5}{\left({{2}}^{{3}}+{{d}}^{{3}}\right)}={5}{\left({2}+{d}\right)}{\left({4}-{2}{d}+{{d}}^{{2}}\right)}\usepackage{cmbright}\Huge\$