Question

Let f(x) be a real -valued function such that f'(x0) = 0 for some x0 ∈ (0, 1), and f"(x0) > 0 for all x ∈ (0, 1). Then f(x) has

Options :

  1. No local minimum in (0, 1)

  2. One local maximum in (0, 1)

  3. Exactly one local minimum in (0, 1)

  4. Two distinct local minimum in (0, 1)

Show Answer

Answer :

Exactly one local minimum in (0, 1)

Solution :

Concept:

Consider a function y = f(x) on a defined interval of x. The function attains extreme values (the value can be maximum or minimum or both).

For maxima:

Local maxima: A point is the local maxima of a function if there is some other point where the maximum value is greater than the local maxima but that point doesn’t exist nearby local maxima.

Global maxima: It is the point where there is no other point has in the domain for which function has more value than global maxima.

For minima:

Local minima: A point is the local minima of a function if there is some other point where the minimum value is less than the local minima but that point doesn’t exist nearby local minima.

Global minima: It is the point where there is no other point has in the domain for which function has less value than global minima.

Stationary Points:

Points where the derivative of the function is zero i.e., f’(x) = 0.

The points can be: Inflection point ,Local maxima, Local minima

Second derivative test: Let the function has a stationary point x = a

if ( d 2 f d x 2 ) x = a < 0  x=-1 and x=2 are extreme points

If ( d 2 f d x 2 ) x = a > 0 then x = a, is a point of minima.

Application:

Given f(x) is a real -valued function such that f'(x0) = 0 for some x0 ∈ (0, 1) Also given f"(x) > 0 for all x ∈ (0, 1) So,

Then f(x) has exactly one local minimum in (0, 1), called the point of minima.

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