x+3是整个作分母吗?
原式=∫（x^3+27-27)dx/(x+3)
=∫(x+3)(x^2-3x+9)dx/(x+3)-27∫d(x+3)/(x+3)
=x^3/3-3x^2/2+9x-27ln|x+3|+C.