Cho hai đa thức: và a) Tính rồi tìm nghiệm của đa thức M (x) b) Tìm đa thức C (x) sao cho C (x) + B(x) = A(x)

b) Ta có $\text{C}\left(\text{x}\right)+\text{B}\left(\text{x}\right)=\text{A}\left(\text{x}\right)$

Suy ra$\text{C}\left(\text{x}\right)=\text{A}\left(\text{x}\right)-\text{B}\left(\text{x}\right)$

$=\left({\text{4x}}^{\text{4}}+{\text{6x}}^{\text{2}}-{\text{7x}}^{\text{3}}-\text{5x}-\text{6}\right)-\left(-{\text{5x}}^{\text{2}}+{\text{7x}}^{\text{3}}+\text{5x}+\text{4}-{\text{4x}}^{\text{4}}\right)$

$={\text{4x}}^{\text{4}}+{\text{6x}}^{\text{2}}-{\text{7x}}^{\text{3}}-\text{5x}-\text{6}+{\text{5x}}^{\text{2}}-{\text{7x}}^{\text{3}}-\text{5x}-\text{4}+{\text{4x}}^{\text{4}}$

$=\left({\text{4x}}^{\text{4}}+{\text{4x}}^{\text{4}}\right)+\left(-{\text{7x}}^{\text{3}}-{\text{7x}}^{\text{3}}\right)+\left({\text{6x}}^{\text{2}}+{\text{5x}}^{\text{2}}\right)+\left(-\text{5x}-\text{5x}\right)+\left(-\text{6}-\text{4}\right)$

$={\text{8x}}^{\text{4}}-{\text{14x}}^{\text{3}}+{\text{11x}}^{\text{2}}-\text{10x}-\text{10}$

 Vậy $C\left(x\right)={\text{8x}}^{\text{4}}-{\text{14x}}^{\text{3}}+{\text{11x}}^{\text{2}}-\text{10x}-\text{10}$