The integral ${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}x(4x^2+2{)}^{3}dx$ can be rewritten as ${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}f(u)du$ by making the substitution $u=4x^2+2.$

What is the function $f(u)?$

$f(u)=$

$a^b$

$sin(a)$

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