My question is about how we determine if the critical number that we found is even or odd?And if we find that the critical number is zero, how can we determine if it's Even or Odd?!Thanks

Example 5 Example 5 f(x) = x\"3 f(x) : x2/3 , _ 1 , 2 f (X) _ 3x2/3 f (K): 3:8/3 The critical values are where The critical values are where the derivative = 0 the derivative = 0 no values of derivative = 0 no values of derivative = O or where the derivative is undefined or where the derivative is undefined , 1 _ . , 2 . _ f (x) = 3x25 Is undefined at x = 0 . f (x) = 3x1/3 5 undefined at x _ 0 so so 0 is an EVEN critical number 0 is an ODD critical number