Answer
$x^3+4x^2+5x+20$
Work Step by Step
Using $(a+b)(c+d)=ab+ad+bc+bd$ or the FOIL Method, the product of the given expression, $
(x+4)(x^2+5)
,$ is
\begin{array}{l}\require{cancel}
x(x^2)+x(5)+4(x^2)+4(5)
\\\\=
x^3+5x+4x^2+20
\\\\=
x^3+4x^2+5x+20
.\end{array}
