Answer
$4x^{2}-21x-18$
Work Step by Step
$(x-6)(4x+3)=$
$...$distribute the second factor, $4x+3$.
$=x(4x+3)-6(4x+3)$
...distribute $x$.
$=4x^{2}+3x-6(4x+3)$
...distribute $-6$.
$=4x^{2}+3x-24x-18$
...gather like terms.
$=4x^{2}-21x-18$