\(B=\left(x-1\right)^3-\left(x+1\right)^3+6\left(x+1\right)\left(x-1\right)\)
\(\Rightarrow B=x^3-3x^2+3x-1-\left(x^3+3x^2+3x+1\right)+6\left(x^2-1\right)\)
\(\Rightarrow B=x^3-3x^2+3x-1-x^3-3x^2-3x-1+6x^2-6\)
\(\Rightarrow B=0-8\)
\(\Rightarrow B=-8\)