Examine the applicable of MVT for all three functions.
f(x)=1−x2 for xϵ[1, 2]
Here, f(x)=1−x2, which is a polynomial function.
Since, a polynomial function is continuous and derivable at all xϵR, therefore
(a) f is continuous in [1, 2]
(b) f is derivable in (1, 2) ⇒ f satisfies conditions of MVT in [1, 2]
Hence, there exists atleast one real cϵ[1, 2] such that
f′(c)=f(2)−f(1)2−1 (∴ f′(c)=−f(b)−f(a)b−a)⇒ −2c=(1−22)−(1−12)2−1 (∵ f(x)=1−x2,∴ f′(x)=−2x)⇒ −2c=−3⇒ c=32 ϵ (1, 2)∴ MVT is verified for the given function in the given interval.