To factor $ x^{3}+4x^{2}+4x+16 $ we can use factoring by grouping:
Group $ \color{blue}{ x^{3} }$ with $ \color{blue}{ 4x^{2} }$ and $ \color{red}{ 4x }$ with $ \color{red}{ 16 }$ then factor each group.
$$ \begin{aligned} x^{3}+4x^{2}+4x+16 = ( \color{blue}{ x^{3}+4x^{2} } ) + ( \color{red}{ 4x+16 }) &= \\ &= \color{blue}{ x^{2}( x+4 )} + \color{red}{ 4( x+4 ) } = \\ &= (x^{2}+4)(x+4) \end{aligned} $$