Originally Posted by

**krystaline86** Okay, so I'm having trouble with subbing in (-)infinity...

a) lim x -> -inf. 1/x^3

= 1/(-inf.)^3

= 1/(-inf.)

= -1/inf.

= 0

Right?

Then consider this...:

b) lim x-> -inf. -1/x^3

= -1/(-inf.)^3

= -1/(-inf.)

= 1/inf. <--- 1) Do the (-)s cancel eachother out here? **I don't think it would really matter if it was negative or not. $\displaystyle \frac{1}{\pm\infty}=0$, whether if it was $\displaystyle +\infty$ or $\displaystyle -\infty$. **

= 0

Right?

Now let's say this was part of a bigger eqn such that the eqn looked like:

lim x-> -inf. of f(x)=(x^3)-**1/(x^3)**

2) Would I have added the zero in my b example, taken it away,

3) Or furthermore, would it be a 0- or 0+?

4) Does it matter since it's a zero and therefore it wouldn't affect the result?

:confused: