分部积分 ：∫ln(1-x)dx=-∫ln(1-x)d(1-x)=-[(1-x)ln(1-x)-∫(1-x)dln(1-x)]=-[(1-x)ln(1-x)-∫(1-x)*1/(1-x) * d(1-x)] =-[(1-x)ln(1-x)+x]=-x-(1-x)ln(1-x)+C=-x+(x-1)ln(1-x)+C