Answer
$x^3-4x^2y+4xy^2-y^3$.
Work Step by Step
The given expression is
$=(x-y)(x^2-3xy+y^2)$
Multiply the right side bracket by each term of the left side bracket.
$=x(x^2-3xy+y^2)-y(x^2-3xy+y^2)$
Clear the parentheses.
$=x^3-3x^2y+xy^2-x^2y+3xy^2-y^3$
Add like terms.
$=x^3-4x^2y+4xy^2-y^3$.