a.\(x+1\cdot x-1\cdot x\)

b.\(60cm{3}\)

• Thương: \(2 x^{2} - 3 x + 1\)
• Dư: \(0\)

5x(4x2−2x+1)−2x(10x2−5x+2)=−36

\(5 x \left(\right. 4 x^{2} - 2 x + 1 \left.\right) = 20 x^{3} - 10 x^{2} + 5 x\) \(2 x \left(\right. 10 x^{2} - 5 x + 2 \left.\right) = 20 x^{3} - 10 x^{2} + 4 x\)

\(20 x^{3} - 10 x^{2} + 5 x - 20 x^{3} + 10 x^{2} - 4 x = - 36\)

\(\left(\right. 20 x^{3} - 20 x^{3} \left.\right) + \left(\right. - 10 x^{2} + 10 x^{2} \left.\right) + \left(\right. 5 x - 4 x \left.\right) = - 36 \Rightarrow x = - 36\)

Vậy

\(\boxed{x = - 36}\)\(\)

P(x)+Q(x)=(x4−x4)+(−5x3)+(3x2)+(4x+2x)+(−5+1)

P(x)+Q(x)=0x4−5x3+3x2+6x−4

b.

R(x)=x4−5x3+4x−5+x4−3x2−2x−1

R(x)=(x4+x4)−5x3−3x2+(4x−2x)−(5+1) \(R \left(\right. x \left.\right) = 2 x^{4} - 5 x^{3} - 3 x^{2} + 2 x - 6\)

R(x)=(x4+x4)−5x3−3x2+(4x−2x)−(5+1) \(R \left(\right. x \left.\right) = 2 x^{4} - 5 x^{3} - 3 x^{2} + 2 x - 6\)