Question bank/JEE Main/Mathematics

JEE MainMathematicsModerateDifferentiation

If differentiable function f(x) is inverse of g(x) then
f^{'}'(g(x)) is equal to

Show answer and solution
f(g(x))=x⇒f′(g(x))⋅g′(x)=1f(g(x)) = x \Rightarrow f^{'}(g(x)) \cdot g^{'}(x) = 1
⇒f′(g(x))=1g′(x)\Rightarrow f^{'}(g(x)) = \frac{1}{g^{'}(x)}
⇒f′′(g(x))⋅g′(x)=−1(g′(x))2g′′(x)\Rightarrow f^{''}(g(x)) \cdot g^{'}(x) = \frac{- 1}{{(g^{'}(x))}^{2}}g^{''}(x)
⇒f′′(g(x))=−g′′(x)(g′(x))3\Rightarrow f^{''}(g(x)) = \frac{- g^{''}(x)}{{(g^{'}(x))}^{3}}

Source: Grass-G / M-12 Mathematics Paper 2 Nov.docx

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