=[3x(x+1)/(x+1)(x²-x+1)]*[(x²+1)/(x²+1)(x²-1)]*(x-1)²/x]=[3x/(x²-x+1)]*[1/(x²-1)]*[(x-1)²/x]=3x(x-1)²/[x(x²-x+1)(x+1)(x-1)]=3(x-1)/[(x²-x+1)(x+1)...