"Verify the hypothesis and conclusion of Lagrange’s mean value theorem for the function
Lagrange’s mean value theorem states that if a function f(x) is continuous on a closed interval [a, b] and differentiable on the open interval (a, b), then there is at least one point x=c on this interval, such that
f(b)−f(a)=f′(c)(b−a)
This theorem is also known as First Mean Value Theorem.
4x – 1>0
∴ f(x) is continuous in [1, 4]
Differentiating with respect to x:
Here,
⇒ 4x – 1>0
∴ f(x) is differentiable in (1, 4)
So both the necessary conditions of Lagrange’s mean value theorem is satisfied.
On differentiating with respect to x:
For f’(c), put the value of x=c in f’(x):
For f(4), put the value of x=4 in f(x):
For f(1), put the value of x=1 in f(x):
⇒ (4c – 1)2 = 45
Hence, Lagrange’s mean value theorem is verified.