\(a.M=\left(x-1\right)^3-4x\left(x+1\right)\left(x-1\right)=3\left(x-1\right)\left(x^2+x+1\right)\)
\(vt=\left(x-1\right)^3-4x\left(x+1\right)\left(x-1\right)\)
\(=\left(x^3-3.x^2.1+3.x.1^2-1^3\right)-\left[4x.x+4x.1+4x.x+4x.\left(-1\right)+x.x+x.\left(-1\right)+1.x+1.\left(-1\right)\right]\)
\(=\left(x^3-3x^2+3x-1\right)-\left(4x^2+4x+4x^2-4x+x^2-x+x-1\right)\)
\(=\left(x^3-3x^2+3x-1\right)-\left(2.4x^2+x^2-1\right)\)
\(=x^3-3x^2+3x-1-8x^2-x^2+1\)
\(=x^3-12x^2\)
\(vp=3\left(x-1\right)\left(x^2+x+1\right)\)
\(=3\left(x^3-1^3\right)\)
\(=3x^3-3\)
\(\Rightarrow M=x^3-12x^2=3x^3-3\)
\(\Rightarrow M=x^3-12x^2-3x^3+3\)
\(\Rightarrow M=-2x^3-12x^2+3\)
\(b.khix=-2,tacó:\)
\(M=-2.\left(-2\right)^3-12.\left(-2\right)^2+3\)
\(=-2.\left(-8\right)-12.4+3\)
\(=16-48+3\)
\(=-29\)
