Question 192006
sometimes  it  is  better  to  add  in  vertical  mode

5y^4  -2y^3  +0y^2  +7y  -11
-5y^4 +0y^3 -1y^2 -8y+6      adding  like  terms

0y^4 -2y^3 -1y^2 -1y -5

or  -2y^3-y^2-y-5