function must exist at that point. That is the first condition a function must pass. So $a=-2$ and $a=2$ are out of the "differentiability selection" game! For the contestants who are left, state the value of the limit for the following points, where the limit does exist. Remember you are looking for the limit of the function at each of these points. What are the close, close, close neighbors of this point telling you the function value should be$?$ Not necessarily what the function value actually is: $a=-3a=-1($hint: what are the close, close neighbors pointing towards?$)a=0a=1($careful here$)a=3$