Answer
$7x^3+3xy^2-3y^3-x^2y$
Work Step by Step
Consider the given polynomial
$(x^3+2xy^2-y^3)-(-6x^3+x^2y-xy^2+2y^3)$
Need to drop the parentheses.
Thus,
$(x^3+2xy^2-y^3)-(-6x^3+x^2y-xy^2+2y^3)=x^3+2xy^2-y^3+6x^3-x^2y+xy^2-2y^3$
or, $=x^3+6x^3-x^2y+2xy^2-y^3+xy^2-2y^3$
or, $=7x^3+3xy^2-3y^3-x^2y$
