Answer
$21x^2-25x-4$
Work Step by Step
Using the Distributive Property and then combining similar terms, the given expression, $
(3x-4)(7x+1)
,$ is equivalent to
\begin{array}{l}\require{cancel}
3x(7x)+3x(1)-4(7x)-4(1)
\\\\=
21x^2+3x-28x-4
\\\\=
21x^2-25x-4
.\end{array}