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MHT CET · Maths · Functions

If the function \(\mathrm{f}(x)=x^3+\mathrm{e}^{\frac{x}{2}}\) and \(\mathrm{g}(x)=\mathrm{f}^{-1}(x)\), then the value of \(g^{\prime}(1)\) is

  1. A 1
  2. B 0
  3. C 2
  4. D \(\frac{1}{2}\)
Verified Solution

Answer & Solution

Correct Answer

(C) 2

Step-by-step Solution

Detailed explanation

\(\begin{array}{ll} & \mathrm{f}(x)=x^3+\mathrm{e}^{\frac{x}{2}} \\ & \Rightarrow \mathrm{f}^{\prime}(x)=3 x^2+\frac{\mathrm{e}^{\frac{x}{2}}}{2} \\ & \text { Given that } \mathrm{g}(x)=\mathrm{f}^{-1}(x) \\ \therefore \quad & \mathrm{gof}(x)=x \\ \therefore \quad & \mathrm{f}(x))=x \\ & \text { Differentiating w.r.t. } x, \text { we get } \\ & \mathrm{g}^{\prime}(\mathrm{f}(x)) \mathrm{f}^{\prime}(x)=1 \\ & \text { for } x=0, \text { we get } \\ & \mathrm{g}^{\prime}(\mathrm{f}(0)) \cdot \mathrm{f}^{\prime}(0)=1 \\ \therefore \quad & \mathrm{~g}^{\prime}(1)=\frac{1}{\mathrm{f}^{\prime}(0)}=\frac{1}{0+\frac{1}{2}}=2\end{array}\)