6(x+1)+2(x-1)(x^2+x+1)-2(x+1)^3=26
6(x^2+2x+1)+2(x-1)(x^2+x+1)-2(x^3+3x^2+3x+1)=0
(6x^2+12x+6)+(2x^3-2)-(2x^3+6x^2+6x+2)=26
6x=24 => x=4
6(x+1)+2(x-1)(x^2+x+1)-2(x+1)^3=26
6(x^2+2x+1)+2(x-1)(x^2+x+1)-2(x^3+3x^2+3x+1)=0
(6x^2+12x+6)+(2x^3-2)-(2x^3+6x^2+6x+2)=26
6x=24 => x=4