If f '(5) = 0 and f ''(5) = 0, what can you say about f ?

A. At x = 5, f has a local maximum.
B. At x = 5, f has a local minimum.
C. At x = 5, f has neither a maximum nor a minimum.
D. More information is needed to determine if f has a maximum or minimum at x = 5.

Respuesta :

Answer:

D)

Step-by-step explanation:

Remember, if a is critical point of f then f'(a)=0. And criterion of the second derivative says that if a is a critical point of f and

1. if [tex]f''(a)<0[/tex] then f has a relative maximum in (a,f(a)),

2. if [tex]f''(a)>0[/tex] then f has a relative minimum in (a,f(a)),

3. if [tex]f''(a)=0,[/tex] Then the criterion does not decide. That is,  f may have a relative maximum at a, a relative minimum at (a, f (a)) or neither.

Since [tex]f'(5)=0[/tex] then 5 is a critical point of f. Now we apply the second criterium:

since [tex]f''(5)=0[/tex] then the criterium doesn't decide, that means, more information is needed to determine if f has a maximum or minimum at x = 5.

Using the concept of critical point and the second derivative test, it is found that the correct option is:

D. More information is needed to determine if f has a maximum or minimum at x = 5.

  • The critical points of a function [tex]f(x)[/tex] are the values of x for which [tex]f^{\prime}(x) = 0[/tex].

Applying the second derivative test, we have that:

  • If positive, that is, [tex]f^{\prime\prime}(x) > 0[/tex], it is a relative minimum.
  • If negative, that is, [tex]f^{\prime\prime}(x) < 0[/tex], it is a relative maximum.
  • If zero, that is, [tex]f^{\prime\prime}(x) = 0[/tex], we do not have sufficient information.

In this problem:

  • [tex]f^{\prime}(5) = 0[/tex], thus, at x = 5 is a critical value.
  • [tex]f^{\prime\prime}(5) = 0[/tex], thus, we need more information, which means that the correct option is:

D. More information is needed to determine if f has a maximum or minimum at x = 5.

A similar problem is given at https://brainly.com/question/16944025