通分，注意到1-x³=(1-x)(1+x+x²)原式=lim(x→1)[(1+x+x²)/(1-x³)-3/(1-x³)]=lim(x→1)(x²+x-2)/(1-x³)=lim(x→1)[(x-1)(x+2)]/[(1-x)(1+x+x²)]= -lim(x→1)(x+2)]/(1+x+x²)= -(1+2)/(1+1+1)= -1
