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KCET · Maths · Permutation Combination

If \( f(x)=x^{3} \) and \( g(x)=x^{3}-4 x \) in \( -2 \leq x \leq 2 \), then consider the statements:
(a) \( f(x) \) and \( g(x) \) satisfy mean value theorem.
(b) \( f(x) \) and \( g(x) \) both satisfy Rolle's theorem.
(c) Only \( g(x) \) satisfies Rolle's theorem.
Of these statements

  1. A (a) alone is cortect
  2. B (a) and (c) are correct.
  3. C (a) and (b) are correct.
  4. D None is correct.
Verified Solution

Answer & Solution

Correct Answer

(B) (a) and (c) are correct.

Step-by-step Solution

Detailed explanation

Given that, \(f(x)=x^{3}\) and \(g(x)=x^{3}-4 x\)
Since, \(f(x)\) and \(g(x)\) are both continuous at \([-2,2]\) and differentiable at \([-2,2]\)
So, \(f(x)\) and \(g(x)\) satisfy mean value theorem.
Now, \(f(-2)=-8, f(2)=8\)
So, \(f(-2) \neq f(2)\)
\(g(2)=(2)^{3}-4(2)=0=g(-2)=(-2)^{3}-4(-2)=0\)
Therefore, \(f(x)\) does not satisfy Rolle's theorem but \(g(x)\) satisfy Rolle's theorem.