Answer
$m^3-3m^2-40m$
Work Step by Step
Using the Distributive Property, the product of the given expression, $
m(m+5)(m-8)
,$ is
\begin{array}{l}\require{cancel}
[m(m)+m(5)](m-8)
\\\\=
[m^2+5m](m-8)
\\\\=
m^2(m)+m^2(-8)+5m(m)+5m(-8)
\\\\=
m^3-8m^2+5m^2-40m
\\\\=
m^3-3m^2-40m
.\end{array}