Answer
$2r^2+3s^2+t^2-7rs+3rt-4st$
Work Step by Step
Using the Distributive Property, the product of the given expression, $
(r-3s+t)(2r-s+t)
,$ is
\begin{array}{l}\require{cancel}
r(2r)+r(-s)+r(t)-3s(2r)-3s(-s)-3s(t)+t(2r)+t(-s)+t(t)
\\\\=
2r^2-rs+rt-6rs+3s^2-3st+2rt-st+t^2
\\\\=
2r^2+3s^2+t^2+(-rs-6rs)+(rt+2rt)+(-3st-st)
\\\\=
2r^2+3s^2+t^2-7rs+3rt-4st
.\end{array}
