Answer:
The sum is -5x^5y - 6xy^3; The difference is 11x^5y - 4x^3y^4 - 8xy^3
Step-by-step explanation:
3x^5y - 2x^3y^4 - 7xy^3
+ -8x^5y + 2x^3y^4 + xy^3
-5x^5y -6xy^3
3x^5y - 2x^3y^4 - 7xy^3 - ( -8x^5y + 2x^3y^4 + xy^3)
Change the signs in the second polynomials when subtracting
3x^5y - 2x^3y^4 - 7xy^3 + ( 8x^5y - 2x^3y^4 - xy^3) =
11x^5y - 4x^3y^4 - 8xy^3