求不定积分x^3/x+1dx
问题描述：
求不定积分x^3/x+1dx
答
=∫(x^3+x^2-x^2-x+x+1-1)/(x+1)dx
=∫(x^2-x+1-1/(x+1))dx
=1/3x^3-1/2x^2+x-ln|x+1|+C