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\$ . The second factor in this answer is missing its middle term. Also, you can see this answer is wrong by multiplying out:

$\displaystyle{\left({3}{x}+{5}\right)}{\left({9}{{x}}^{{2}}+{25}\right)}={3}{x}\cdot{9}{{x}}^{{2}}+{3}{x}\cdot{25}+{5}\cdot{9}{{x}}^{{2}}+{5}\cdot{25}={27}{{x}}^{{3}}+{75}{x}+{45}{{x}}^{{2}}+{125}\usepackage{cmbright}\Huge\$