Find the value of c prescribed by Lagrange’s mean value theorem for the function defined on [2, 3].


f(x) will exist, if


x2 – 4 ≥ 0


x2 ≥ 4


x ≤ -2 or x ≥ 2


for each x Є [2, 3], the function f(x) has a unique definite value, f(x) is continuous on (2, 3).




Exists for all x Є (2, 3).


So, f(x) is differentiable on (2,3).


Hence, both the conditions of Lagrange’s Theorem are satisfied.


Consequently, there exists c Є (2, 3) such that,










0






Squaring both sides,




5x2 – 20 – x2 = 0


4x2 = 20


x2 = 5


x = ± √5


Hence, c = √5 Є (2, 3) such that


Hence the above explanation verifies the Lagrange’s Theorem.


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