Answer
$xy^4(x-2y+3x^2y^2)$
Work Step by Step
The $GCF$ of the terms is $
xy^4
$ since it is the highest expression that can evenly divide (no remainder) all the given constants.
Factoring the $GCF,$ the given expression is equivalent to
\begin{array}{l}\require{cancel}
x^2y^4-2xy^5+3x^3y^6
\\\\=
xy^4(x-2y+3x^2y^2)
.\end{array}