# Verify Lagrange’s mean value theorem for the following functions : f(x) = 2x – x2, x ∈ [0, 1]. - Mathematics and Statistics

Sum

Verify Lagrange’s mean value theorem for the following functions : f(x) = 2x – x2, x ∈ [0, 1].

#### Solution

The function f given as f(x) = 2x – x2  is a polynomial function. Hence, it is continuous on [0, 1] and differentiable on (0, 1).

Thus, the function f satisfies the conditions of Lagrange’s mean value theorem.

∴ there exists c ∈ (0, 1) such that

f'(c) = (f(1) - f(0))/(1 - 0)                    ...(1)

Now, f(x) = 2x – x2
∴ f(0) = 0 – 0 = 0
and
f(1) = 2(1) – 12 = 1

Also, f'(x) = d/dx(2x - x^2)

= 2 x 1 – 2x
= 2 – 2x
∴ f'(c) = 2 – 2c
∴ from (1), 2 – 2c

= (1 - 0)/(1)
= 1
∴ 2c = 1

∴ c = (1)/(2) ∈ (0 , 1)
Hence, Lagrange’s mean value theorem is verified.

Concept: Lagrange's Mean Value Theorem (Lmvt)
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#### APPEARS IN

Balbharati Mathematics and Statistics 2 (Arts and Science) 12th Standard HSC Maharashtra State Board
Chapter 2 Applications of Derivatives
Exercise 2.3 | Q 7.4 | Page 80