Chapter 4: Problem 16
Find the derivative of each function. $$ f(x)=\ln \left(e^{x}-2 x\right) $$
Short Answer
Expert verified
\( f'(x) = \frac{e^x - 2}{e^x - 2x} \)
Step by step solution
01
Identify the Outer Function
The given function is \( f(x) = \ln(e^x - 2x) \). Here, the outer function is the natural logarithm function \( g(u) = \ln(u) \), where \( u = e^x - 2x \).
02
Differentiate the Outer Function Using Chain Rule
According to the chain rule, the derivative of \( f(x) = g(u(x)) \) is \( f'(x) = g'(u) \cdot u'(x) \). The derivative of \( g(u) = \ln(u) \) is \( g'(u) = \frac{1}{u} \). So, \( g'(e^x - 2x) = \frac{1}{e^x - 2x} \).
03
Differentiate the Inner Function
Next, we need the derivative of the inner function \( u(x) = e^x - 2x \). The derivative of \( e^x \) is \( e^x \) and the derivative of \( -2x \) is \(-2\). Therefore, \( u'(x) = e^x - 2 \).
04
Combine Using the Chain Rule
Using the results from Steps 2 and 3, substitute back into the chain rule formula. We have \( f'(x) = \frac{1}{e^x - 2x} \cdot (e^x - 2) \).
05
Simplify the Expression
Simplify the expression to get the final answer: \( f'(x) = \frac{e^x - 2}{e^x - 2x} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chain Rule
The Chain Rule is a powerful tool in calculus for finding the derivative of composite functions. A composite function is simply when you have one function nested inside another function. For example, in this exercise, the function given is a natural logarithm of another function:
- The outer function is the natural logarithm, expressed as \( g(u) = \ln(u) \).
- The inner function is \( u(x) = e^x - 2x \).
- Find the derivative of the outer function: \( g'(u) = \frac{1}{u} \).
- Evaluate it at the inner function, so \( g'(u) = \frac{1}{e^x - 2x} \).
- Find the derivative of the inner function: \( u'(x) = e^x - 2 \).
- Combine them using the Chain Rule formula: \( f'(x) = \frac{1}{e^x - 2x} \cdot (e^x - 2) \).
Natural Logarithm
The natural logarithm, denoted as \( \ln(x) \), is a special function in calculus. It's the inverse of the exponential function with base \( e \), which is approximately 2.718. Understanding how to differentiate the natural logarithm is essential in calculus as it often appears in exponential growth and decay problems.
Key Properties of Natural Logarithm:
By studying the logarithmic rules, you can confidently approach derivatives involving natural logs by focusing on how the logarithm changes relative to its input function.
Key Properties of Natural Logarithm:
- If \( y = \ln(x) \), then the derivative \( \frac{dy}{dx} = \frac{1}{x} \).
- This relationship shows how the rate of change of \( \ln(x) \) depends on \( x \).
By studying the logarithmic rules, you can confidently approach derivatives involving natural logs by focusing on how the logarithm changes relative to its input function.
Differentiation
Differentiation is a core concept in calculus and represents finding the rate at which a function changes at any point. It's an essential skill for understanding gradients, slopes, and rates in various contexts, from physics to economics.
Differentiation Basics:
Differentiation Basics:
- The derivative of a function represents its slope at a given point \( x \).
- Common functions, like polynomials and exponentials, have well-known derivative rules.
- The derivative of \( e^x \) is \( e^x \) itself.
- The derivative of \(-2x\) is \(-2\).