I'm having a hard time understanding the solution to this problem.  

How is it that, for some general variable '$c$', the limit is always positive infinity, except for the case where $c = 1$?  

If $c = 0$, shouldn't the limit be negative infinity?  

Further, what about $c = -1$?

[![enter image description here](https://i.stack.imgur.com/Nfi0z.png)](https://i.stack.imgur.com/Nfi0z.png)