P(x)+Q(x)+R(x)=(3x4−2x2+8x10)+(4x3−6x2+7x−1)+(−3x4+5x2−8x−5)
=[3x4−2x2+8x10+(−3x4+5x2−8x−5)]+4x3−6x2+7x−1
=3x2−15+4x3−6x2+7x−1=4x3−3x2+7x−16
P(x)−Q(x)−R(x)=(3x4−2x2+8x10)−(4x3−6x2+7x−1)−(−3x4+5x2−8x−5)
=6x4−4x3−x2+9x−4