Second derivative of an exponential function

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SUMMARY

The discussion focuses on finding the second derivative of the function f'(x) = [1/(1+kx)^2]e^[x/(1+kx)], where k is a positive constant. The correct second derivative is established as f''(x) = [1/(1+kx)^4]e^[x/(1+kx)] + e^[x/(1+kx)] . [-2k/(1+kx)^3]. Participants emphasize the importance of applying the product and quotient rules of differentiation correctly, especially when coefficients are functions of x rather than constants.

PREREQUISITES
  • Understanding of basic calculus, specifically differentiation rules.
  • Familiarity with the product and quotient rules of derivatives.
  • Knowledge of exponential functions and their derivatives.
  • Ability to manipulate algebraic expressions involving functions of x.
NEXT STEPS
  • Review the product rule and quotient rule in calculus.
  • Study the differentiation of exponential functions with variable coefficients.
  • Practice finding higher-order derivatives of composite functions.
  • Explore applications of derivatives in real-world scenarios, particularly in physics and engineering.
USEFUL FOR

Students studying calculus, particularly those focusing on differentiation techniques, as well as educators looking for examples of common misconceptions in derivative calculations.

Calculus :(
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Homework Statement


I have the derived function:
f'(x) = [1/(1+kx)^2]e^[x/(1+kx)]
k is a positive constant


Homework Equations


I need to find the second derivative, which I thought was just the derivative of the exponent multiplied by the coefficient (as you find the first derivative), but the answers say:

f''(x) = [1/(1+kx)^4]e^[x/(1+kx)] + e^[x/(1+kx)] . [-2k/(1+kx)^3]

The Attempt at a Solution


All I managed to get was:
f''(x) = [1/(1+kx)^4]e^[x/(1+kx)]

 
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Calculus :( said:

Homework Statement


I have the derived function:
f'(x) = [1/(1+kx)^2]e^[x/(1+kx)]
k is a positive constant


Homework Equations


I need to find the second derivative, which I thought was just the derivative of the exponent multiplied by the coefficient (as you find the first derivative), but the answers say:

f''(x) = [1/(1+kx)^4]e^[x/(1+kx)] + e^[x/(1+kx)] . [-2k/(1+kx)^3]

The Attempt at a Solution


All I managed to get was:
f''(x) = [1/(1+kx)^4]e^[x/(1+kx)]

You say "I thought was just the derivative of the exponent multiplied by the coefficient (as you find the first derivative)...", but THAT is not true: it is true ONLY if the "coefficient" of the exponential is a constant. If the coefficient itself is a function of x it will not work. Go back and review some basic properties of derivatives.
 
Calculus :( said:

Homework Statement


I have the derived function:
f'(x) = [1/(1+kx)^2]e^[x/(1+kx)]
k is a positive constant


Homework Equations


I need to find the second derivative, which I thought was just the derivative of the exponent multiplied by the coefficient (as you find the first derivative), but the answers say:

f''(x) = [1/(1+kx)^4]e^[x/(1+kx)] + e^[x/(1+kx)] . [-2k/(1+kx)^3]
##\frac{df}{dx}=\frac{e^{\frac{x}{1+kx}}}{(1+kx)^2}##. You have the quotient of two functions of ##x##. You can't just take the derivative of the exponential term. What do you do when you have a product or quotient of functions?
 

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