Absolute extrema are nothing more than the largest/smallest values the function takes on a certain domain. There are two possibilities: these values lie at the edge of the domain of interest, or there is a minimum/maximum within it.

1) Find f(-2) and f(2).

2) Find f'(x)=0 and solve for x= a,b,c,d Then find f(a), f(b), f(c), f(d).

The answer is the greatest and least of these.