Cho hai đa thứcP(x) = 2x3 - 3x + x5 - 4x3 + 4x - x5 + x2 - 2; Q(x) = x3 - 2x2 + 3x + 1 + 2x2Tính P(x) - Q(x)

Ta có

P(x)=2x3−3x+x5−4x3+4x−x5+x2−2=x5−x5+2x3−4x3+x2+(4x−3x)−2=−2x3+x2+x−2 Và Q(x)=x3−2x2+3x+1+2x2

=x3+-2x2+2x2+3x+1=x3+3x+1

Khi đó

P(x)−Q(x)=−2x3+x2+x−2−x3+3x+1=−2x3+x2+x−2−x3−3x−1=−2x3−x3+x2+(x−3x)−2−1=−3x3+x2−2x−3

Chọn đáp án B