Answer
$x^3+5x^2+3x+15$
Work Step by Step
Using $(a+b)(c+d)=ab+ad+bc+bd$ or the FOIL Method, the product of the given expression, $
(x+5)(x^2+3)
,$ is
\begin{array}{l}\require{cancel}
x(x^2)+x(3)+5(x^2)+5(3)
\\\\=
x^3+3x+5x^2+15
\\\\=
x^3+5x^2+3x+15
.\end{array}
