Graph this piecewise function and use it to determine the values of a for which the l

I'm supposed to graph this piecewise function and use it to determine the values of a for which the limit of f(x) exists as x approaches a.

http://www2.wolframalpha.com/Calcula...21&w=399&h=188

I'm not entirely sure how to start this question. Looking on the graph I'm thinking the only place where the limit of f(x) as x approaches a doesn't exist is -1 and 1. Could someone please explain? (Worried)

That is the graph. So does the limit of f(x) as x approaches a exist everywhere except 1 and -1 ?(Worried)