Rút gọn:
\(=\dfrac{1}{x^2+x+1}+\dfrac{1}{x\left(x-1\right)}-\dfrac{2x}{x^3-1}\)
\(=\dfrac{1}{x^2+x+1}+\dfrac{1}{x\left(x-1\right)}-\dfrac{2x}{\left(x-1\right)\left(x^2+x+1\right)}\)
\(=\dfrac{x^2-x}{x\left(x-1\right)\left(x^2+x+1\right)}+\dfrac{x^2+x+1}{x\left(x-1\right)\left(x^2+x+1\right)}-\dfrac{2x^2}{x\left(x-1\right)\left(x^2+x+1\right)}\)
\(=\dfrac{x^2-x+x^2+x+1-2x^2}{x\left(x-1\right)\left(x^2+x+1\right)}\)\(=\dfrac{1}{x\left(x-1\right)\left(x^2+x+1\right)}\)\(=\dfrac{1}{x^4-x}\)
thay x =2 vào bt P, ta có:
\(\dfrac{1}{2^4-2}\)\(=\dfrac{1}{14}\)
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