a) Ta có: F(x) + H(x) = 0.
Suy ra: H(x)=−(2x4−x3+x−3)=−2x4+x3−x+3
b) Ta có: K(x) - G(x) = F(x)
Suy ra K(x)=F(x)+G(x)=2x4−x3+x−3−x3+5x2+4x+2=2x4−2x3+5x2+5x−1