Well you have to make the powers line up so we know r^4 is the highest and you work your way down so
0r^4-5r^3-4r^2-3r
R^4+0r^3-4r^2+3r
So now that they are lined up by power we solve (keep in mind that the 0r's are place holders and have no value)
R^4-5r^3-8r^2
That's your answer
