Answer
$(4xy^3)(xy^2-2)$
Work Step by Step
The student was wrong because he was not ave to completely factor the given polynomial.
In his answer, $2xy^3(2xy^2-4)$, the terms of the binomial factor have a common factor of $2$.
Factoring out the $2$ gives:
$=(2xy^3)(2)(xy^2-2)
\\=(4xy^3)(xy^2-2)$
