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