x^3-1/x^2+x+1 + x^3+1/x^2-x+1 + 2x^2/1-x
=(x-1)(x^2+x+1)/(x^2+x+1)+(x+1)(x^2-x+1)/(x^2-x+1)+2x^2/(1-x)
=x-1+x+1+2x^2/(1-x)
=2x+2x^2/(1-x)
=[2x-2x^2+2x^2)/(1-x)
=2x/(1-x)