Analyzing functions max and min

Question

What are the critical values on the graph of y = x³ - 12x + 1? 

Choices:

1. x = -2, 0, 2
2. x = -2, 2
3. x = -4, 4
4. x = -3.42, 0, 3.42

Answer 1

y = x³ - 12x + 1

to find critical values, take the 1st derivative, and set = to 0:

y' = 3x² - 12 = 0

y = +2, -2