5x(4x2−2x+1)−2x(10x2−5x+2)=−36 

5x.4x2+5x.(−2x)+5x.1+(−2x).10x2+(−2x).(−5x)+(−2x).2=−365x.4x2+5x.(−2x)+5x.1+(−2x).10x2+(−2x).(−5x)+(−2x).2=−36 

20x3+(−10x2)+5x+(−20x3)+10x2+(−4x)=−3620x3+(−10x2)+5x+(−20x3)+10x2+(−4x)=−36

(20x3−20x3)+(−10x2+10x2)+(5x−4x)=−36(20x3−20x3)+(−10x2+10x2)+(5x−4x)=−36

x=−36x=−3

a. \(x4−5x3+4x−5−x4+3x2+2x+1x4−5x3+4x−5−x4+3x2+2x+1\)

\(=−5x3+3x2+6x−4=−5x3+3x2+6x−4\)

b. \(R(x)=x4−5x3+4x−5−(−x4+3x2+2x+1)R(x)=x4−5x3+4x−5−(−x4+3x2+2x+1)\)

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

\(=2x4−5x3−3x2+2x−6=2x4−5x3−3x2+2x−6\)

a,biểu thức tính thể tích của HHCN là: x.x+1.x-1

b,thể tích của HHCN là:4.4+1.4-1=14