$\text{Có: E(x) = H(x) + K(x)}$
$\text{E(x) = ($7x^{4}$ + $3x^{5}$ - $2x^{2}$ - 4 - $7x^{5}$ + 3) + ($4x^{3}$ - $2x^{2}$ + $3x^{5}$ - $4x^{3}$ + $2x^{4}$ - 6)}$
$\text{E(x) = $7x^{4}$ + $3x^{5}$ - $2x^{2}$ - 4 - $7x^{5}$ + 3 + $4x^{3}$ - $2x^{2}$ + $3x^{5}$ - $4x^{3}$ + $2x^{4}$ - 6}$
$\text{E(x) = $-x^{5}$ + $9x^{4}$ - $4x^{2}$ - 7}$