∫x/(x³+x+1)dx
=∫(x+1)-1/〔(1+x)(x²-x+1 )+x〕dx
=∫1/(x²-x+1)dx-∫1/x dx
=∫1/〔(x-1/2)²+3
/4〕dx+∫1/x dx
=4/3∫1/〔(2x/√3-1/√3)²+1 〕dx+∫1/x dx
=4/3arctan〔(2x-1)/√3〕+ln|x|+C
∫x/(x³+x+1)dx
=∫(x+1)-1/〔(1+x)(x²-x+1 )+x〕dx
=∫1/(x²-x+1)dx-∫1/x dx
=∫1/〔(x-1/2)²+3
/4〕dx+∫1/x dx
=4/3∫1/〔(2x/√3-1/√3)²+1 〕dx+∫1/x dx
=4/3arctan〔(2x-1)/√3〕+ln|x|+C