1/(x-1)-6/(1-x³)=(x-1)/(x²+x+1)
(x²+x+1)/(x³-1)+6/(x³-1)=(x-1)²/(x³-1)
(x²+x+1)+6=(x-1)²
x²+x+7= x²-2x+1
3x=-6
x=-2