limX趋于-1（1/X+1-3/X^3+1）等于多少?
问题描述：
limX趋于-1（1/X+1-3/X^3+1）等于多少?
答
1/(X+1)-3/(X^3+1)
=1/(X+1)-3/(X+1)(X^2-X+1)
=(X^2-X-2)/(X+1)(X^2-X+1)
=(X+1)(X-2)/(X+1)(X^2-X+1)
=(X-2)/(X^2-X+1) (X不等于-1时)
所以：limX 趋于-1 (1/(X+1)-3/(X^3+1))=(-3)/(1+1+1)=-1.
答
同学,先通分的（x^2-x-2）/(x^3+1)=(x-2)(x+1)/(x+1)(x^2-x+1)=
(x-2)/)(x^2-x+1)
极限值等于-1