就是有理函数的积分原式=∫(x^3+x-x)/(x^2+1)dx=∫xdx-∫x/(x^2+1)dx=x^2/2-1/2∫d(x^2+1)/(x^2+1)=x^2/2-1/2ln|x^2+1|+C=x^2/2-ln√(x^2+1)+C
