Multiple Choice

$6$ points

$(02\mathrm{.}05$ MC$)$

Let $f$ and $g$ be functions of $x,$ where $a$ is an unnown constant. What is a valid expression for $\text{'}$ if $f=ax$ and $g=\frac{4x^3+1}{x}?$

$\frac{a}{6x}$

$\frac{-4a{x}^4+2ax}{(4x^3+1{)}^2}$

$\frac{12x^2-2ax}{(4x^3+1{)}^2}$

$\frac{6a{x}^4-1}{x^2}$