Finding locations of absolute extrema

Trying to review for my test next week and this is an example problem that I have a feeling will be on the test yet I am somewhat lost on how to solve. Thanks in advance for the help!

Find the locations of all absolute extrema for the function....

f(x) = 2x^3 + 3x^2 -36x +12 with the domain [ -2, 4 ]

I know I'm supposed to use the first derivative test correct?

f'(x) = 6x^2 + 6x - 36

0 = 6x^2 + 6x - 36

Could someone please solve it from here(assuming I am right so far)?