\(=\dfrac{x^2\left(x^3-1\right)+\left(x^2-1\right)\left(x^2+1\right)}{x^3-1}\)
\(=\dfrac{x^2\left(x-1\right)\left(x^2+x+1\right)+\left(x-1\right)\left(x^3+x^2+x+1\right)}{x^3-1}\)
\(=\dfrac{x^2\left(x^2+x+1\right)+x^3+x^2+x+1}{x^2+x+1}\)
\(=x^2+x+\dfrac{1}{x^2+x+1}\)