\[a^{3} + 8b^{3} + a^{2} + 4ab + 4b^{2} =\]
\[= \left( a^{3} + 8b^{3} \right) + \left( a^{2} + 4ab + 4b^{2} \right) =\]
\[= (a + 2b)\left( a^{2} - 2ab + 4b^{2} \right) + (a + 2b)^{2} =\]
\[= (a + 2b)\left( a^{2} - 2ab + 4b^{2} + a + 2b \right).\]