Answer
$2x^2+9x+4$
Work Step by Step
Using $(a+b)(c+d)=ac+ad+bc+bd$ or the Distributive Property, the given expression, $
(2x+1)(x+4)
,$ is equivalent to
\begin{array}{l}\require{cancel}
2x(x)+2x(4)+1(x)+1(4)
\\\\=
2x^2+8x+1x+4
\\\\=
2x^2+9x+4
.\end{array}