Question Details

What is the relation between f(a) and f(h) according to another form of Rolle’s theorem?

Options

A

f(a) < f(a+h)

B

f(a) = f(a+h)

C

f(a) = f(a-h)

D

f(a) > f(a+h)

Correct Answer :

f(a) = f(a+h)

Solution :

The correct option is f(a) = f(a+h).

To understand why this is correct, let us recall the standard statement of Rolle's Theorem and see how it is adapted to an alternative form.

1. Classical Rolle's Theorem:
If a real-valued function f is:
(i) continuous on a closed interval [a,b],
(ii) differentiable on the open interval (a,b), and
(iii) satisfies the condition that the function values at the endpoints are equal, i.e.,

f(a)=f(b)

then there exists at least one point c(a,b) such that f(c)=0.

2. Alternative Form of Rolle's Theorem:
We can express the interval [a,b] in terms of a starting point a and a positive width h. Let us define the upper bound of the interval as:

b=a+h

Substituting this value of b into the classical interval gives us the interval [a,a+h].

Under this formulation, the third condition of Rolle's Theorem, which requires the function values at the endpoints of the interval to be equal (f(a)=f(b)), directly translates to:

f(a)=f(a+h)

Consequently, if this relation holds along with continuity and differentiability on the interval, there exists a number θ (where 0<θ<1) such that the derivative vanishes at the point a+θh, meaning f(a+θh)=0.

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