(1 pt) Find all critical values for the function

Question

f(x) = 6 x^3 - 18 x + 1,
and then list them (separated by commas) in the box below.

List of critical numbers:

Answer 1

critical values are where f' = 0 or undefined.
f'(x) = 18x^2-18 = 18(x^2-1)

So, where is f' = 0?