How do you simplify 8x (x^3 + 2x^2 + x) + 4x (x^2 - x + 4)?

$8 x \left({x}^{3} + 2 {x}^{2} + x\right) + 4 x \left({x}^{2} - x + 4\right)$ = $8 {x}^{4} + 16 {x}^{3} + 8 {x}^{2} + 4 {x}^{3} - 4 {x}^{2} + 16 x$
= $8 {x}^{4} + 20 {x}^{3} + 4 {x}^{2}$ = $4 {x}^{2} \left(2 {x}^{2} + 5 x + 1\right)$