答：
(3x^4+2x^2)/(x^2+1)
=[3(x^2+1)x^2-(x^2+1)+1]/(x^2+1)
=3x^2-1+1/(x^2+1)
∫((3x^4+2x^2)/(x^2+1))dx
=∫(3x^2-1)dx+∫[1/(x^2+1)]dx
=x^3-x+arctanx+C