\[x^{7} + x^{3} + 4x^{4} + 4 =\]
\[= x^{3}\left( x^{4} + 1 \right) + 4 \cdot \left( x^{4} + 1 \right) =\]
\[= (x^{4} + 1)(x^{3} + 4)\]