Answer
$5x^4+5x^2+x+5$
Work Step by Step
Removing the grouping symbols and then combining like terms, the given expression, $
\left( x^4+\dfrac{2}{3}x+5 \right)+\left( 4x^4+5x^2+\dfrac{1}{3}x \right)
,$ simplifies to
\begin{array}{l}
x^4+\dfrac{2}{3}x+5+4x^4+5x^2+\dfrac{1}{3}x
\\\\=
(x^4+4x^4)+5x^2+\left( \dfrac{2}{3}x+\dfrac{1}{3}x \right)+5
\\\\=
5x^4+5x^2+x+5
.\end{array}
