~ Bạn tham khảo ~
`B = (x - 1)^3 - (x + 1)^3 + 6(x + 1)(x -1)`
`<=> B = (x-1-x-1)[(x-1)^2 + (x-1)(x+1) + (x+1)^2] + 6(x^2 - 1^2)`
`<=> B = -2(x^2-2x+1+x^2-1+x^2+2x+1) + 6x^2 - 6`
`<=> B = -2(3x^2+1) + 6x^2 - 6`
`<=> B = -6x^2 - 2 + 6x^2 - 6`
`<=> B = -8`
Vậy `B=-8`