1. Okey, i'm confused again.... So this function doesn't have a critical number. I should choose an answer E) as none of these???

2. Originally Posted by Samantha
Okey, i'm confused again.... So this function doesn't have a critical number. I should choose an answer E) as none of these???
As no correct answer is listed, "none of these" is the most correct answer. So yes.

-Dan

3. Originally Posted by Plato
Definitions do differ. In North America it is common to see the following:
A critical number of a function f is a number c in the domain of f at which f ’(c)=0 or f ’(c) does not exist.
Hello,

I'm only curious and this post has nothing to do with Samantha's problem.

If I take the definition I get:

1. c belongs to the domain
2. A critical number exists if f'(x) doesn't exist.

In my opinion this takes place with functions like: $\displaystyle f(x) = | x |$

1. $\displaystyle 0 \in \mathbb{R}$
2. $\displaystyle f(0) = 0$ exists
3. f'(0) doesn't exist. Thus x = 0 is a critical number

Do I get this right?

4. Yes, that is the way the definition is used here.
0 is in the domain of $\displaystyle f$ and $\displaystyle f'(0)$ does not exist.

5. Originally Posted by Samantha
Okey, i'm confused again.... So this function doesn't have a critical number. I should choose an answer E) as none of these???
What textbook is being used in the course?
How does it define a critical number?
If you are using one of the major texts that I listed above, the answer is E.
BUT, you text may not agree with any of the major texts.

6. Originally Posted by Plato