JEE Main 2020MathematicsDifferentiationHardMCQ

JEE Main 2020 — Differentiation Question with Solution

JEE Main 2020 (09 Jan Shift 2)

Question

Let f and g be differentiable functions on R such that fog is the identity function. If for some a,b∈R,g'a=5 and ga=b, then f'b is equal to:

Choose an option

Show full solutionCorrect option: A
Correct answer
A15

Step-by-step explanation

fgx=x

⇒f'gx.g'x=1

Put x=a

⇒f'gag'a=1

⇒f'b×5=1

⇒f'b=15

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About this question

This is a previous-year question from JEE Main 2020, covering the Differentiation chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.