Ta có P(x)=(5x4+2x)+(−3x2+7x−5)−(5x4+2x)
=(5x4−3x2+2x)+(−5x4−2x+7x−5)
=M(x) +N(x)
Với M(x)=(5x4−3x2+2x), N(x)=−5x4−2x+7x−5