Answer
$(4x-1)(x^2-3)$
Work Step by Step
Using factoring by grouping, the given expression, $
4x^3-x^2-12x+3
,$ is equivalent to
\begin{array}{l}\require{cancel}
(4x^3-x^2)-(12x-3)
\\\\=
x^2(4x-1)-3(4x-1)
\\\\=
(4x-1)(x^2-3)
.\end{array}