Answer
$5x^3+3x^2y-4y^3-xy^2$
Work Step by Step
Consider the given polynomial
$(x^3+2x^2y-y^3)-(-4x^3-x^2y+xy^2+3y^3)$
Need to drop the parentheses.
Thus,
$(x^3+2x^2y-y^3)-(-4x^3-x^2y+xy^2+3y^3)=x^3+2x^2y-y^3+4x^3+x^2y-xy^2-3y^3$
or, $=x^3+4x^3+2x^2y+x^2y-xy^2-4y^3$
or, $=5x^3+3x^2y-4y^3-xy^2$
