\(\)

\(\)

a) V=x(x−1)(x+1)=x3−x

b) Tại \(x=4\), thể tích của hình hộp chữ nhật là:

\(x=4^3-4=60\) (đơn vị thể tích\(\)

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

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

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

\(x=-36\)

Vậy \(x=-36\).

\(=x^4-5x^3+4x-5-x^4+3x^2+2x+1\)

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

\(=-5x^3+3x^2+6x-4\)

b) \(\)

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

\(=x^4-5x^3+4x-5+x^4-3x^2-2x-1\)

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

\(=2x^4-5x^3-3x^2+2x-6\)