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CUET · MATHS · PYQ PAPER 2023

If \(f(x)\) and \(g(x)\) are continuous functions and \(f \circ g\) is an identity function such that \(g^{\prime}(b)=5\) and \(g(b)=a\), then \(f(a)\) is :

  1. A \(\frac{2}{5}\)
  2. B \(\frac{1}{5}\)
  3. C \(\frac{3}{5}\)
  4. D 5
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{1}{5}\)

Step-by-step Solution

Detailed explanation

Given \(f(g(x)) = x\) \(f'(g(x)) \cdot g'(x) = 1\) Substitute \(x=b\): \(f'(g(b)) \cdot g'(b) = 1\) Substitute \(g(b)=a\) and \(g'(b)=5\): \(f'(a) \cdot 5 = 1\) \(f'(a) = \frac{1}{5}\)