计算：limx→-1[1/(x+1)-3/(x3+1)]

计算：limx→-1[1/(x+1)-3/(x3+1)]
【正确答案】：1/(x+1)-3/(x3+1)=(x+1)(x-2)/(x3+1)=(x-2)/(x2-x+1) 故所求极限等于limx→-1（1/(x+1)-3/(x3+1)=(-1-2)/(-1)2-(-1)+1=-1