(x^2-1)^3=(x^2-1)(x^2-1)(x^2-1)(x2−1)3=(x2−1)(x2−1)(x2−1)
(x^2-1)(x^2-1)=x^4-2x^2+1(x2−1)(x2−1)=x4−2x2+1
(x^4-2x^2+1)(x^2-1)=x^6-2x^4+x^2-x^4+2x^2-1(x4−2x2+1)(x2−1)=x6−2x4+x2−x4+2x2−1
=x^6-3x^4+3x^2-1=x6−3x4+3x2−1
[(x^2-1)^3(2x+1)]=(x^6-3x^4+3x^2-1)(2x+1)[(x2−1)3(2x+1)]=(x6−3x4+3x2−1)(2x+1)
=2x^7-6x^5+6x^3-2x+x^6-3x^4+3x^2-12x7−6x5+6x3−2x+x6−3x4+3x2−1
=2x^7+x^6-6x^5-3x^4+6x^3+3x^2-2x-12x7+x6−6x5−3x4+6x3+3x2−2x−1