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Let f : R ^(+) to R defined as f (x)= e ...

Let `f : R ^(+) to R` defined as `f (x)= e ^(x) + `ln x and `g = f ^(-1)` then correct statement (s) is/are:

A

`g''(e)=(1-e)/((1+e)^(3))`

B

`g ''(e) (e-1)/((1+e)^(3))`

C

`g '(e) =e+1`

D

`g '(e) =(1)/(e+1)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the function \( f(x) = e^x + \ln x \) and its inverse \( g = f^{-1} \). We will find the first and second derivatives of \( g \) at a specific point, which is \( e \). ### Step 1: Find \( g(e) \) Since \( g \) is the inverse of \( f \), we need to find \( g(e) \) by solving \( f(x) = e \). \[ f(x) = e^x + \ln x = e \] We can check for \( x = 1 \): \[ f(1) = e^1 + \ln 1 = e + 0 = e \] Thus, \( g(e) = 1 \). ### Step 2: Find \( g'(x) \) Using the formula for the derivative of the inverse function, we have: \[ g'(x) = \frac{1}{f'(g(x))} \] Substituting \( x = e \): \[ g'(e) = \frac{1}{f'(g(e))} = \frac{1}{f'(1)} \] ### Step 3: Find \( f'(x) \) Now we calculate \( f'(x) \): \[ f'(x) = \frac{d}{dx}(e^x + \ln x) = e^x + \frac{1}{x} \] Evaluating at \( x = 1 \): \[ f'(1) = e^1 + \frac{1}{1} = e + 1 \] Thus, \[ g'(e) = \frac{1}{e + 1} \] ### Step 4: Find \( g''(x) \) Using the formula for the second derivative of the inverse function: \[ g''(x) = -\frac{f''(g(x))}{(f'(g(x)))^3} \] Substituting \( x = e \): \[ g''(e) = -\frac{f''(g(e))}{(f'(g(e)))^3} = -\frac{f''(1)}{(f'(1))^3} \] ### Step 5: Find \( f''(x) \) Now we calculate \( f''(x) \): \[ f''(x) = \frac{d}{dx}(f'(x)) = \frac{d}{dx}(e^x + \frac{1}{x}) = e^x - \frac{1}{x^2} \] Evaluating at \( x = 1 \): \[ f''(1) = e^1 - \frac{1}{1^2} = e - 1 \] ### Step 6: Calculate \( g''(e) \) Now we can substitute \( f''(1) \) and \( f'(1) \) into the equation for \( g''(e) \): \[ g''(e) = -\frac{e - 1}{(e + 1)^3} \] ### Conclusion The correct statements regarding \( g'(e) \) and \( g''(e) \) can be derived from the above calculations.
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