Add the Polynomials 27.) 3y - 5 and 7y +8

28.) - 8xy - 4 and xy - 1

29.) 5a^3 -3a +7 and 7a^3 - 10a -8

30.) - 6x^3y + x^2 y^2 - 5xy and 8 x^3y - 10x^2 y^2 + 6

31.) x^2 -2x + 1 and x^4 + x^3 -x^2 + 5

32.) a^3b^2 - a^2b^3 and a^3b^2 - 5a^2b^3 + 7