a. R(x)+S(x) = (−8x4+6x3+2x2−5x+1)+(x4−8x3+2x+3)
= −7x4−2x3+2x2−3x+4
b. R(x) - S(x) = (−8x4+6x3+2x2−5x+1)−(x4−8x3+2x+3)
= −9x4+14x3+2x2−7x−2