Chapter 3: Problem 38
In Exercises \(37-42,\) find \(f^{\prime}(x)\) and state the domain of \(f^{\prime}\) $$f(x)=\ln (2 x+2)$$
Short Answer
Expert verified
The derivative of the function is \(f^{\prime}(x) = \frac{1}{x+1}\) and its domain is \(x \in (-\infty, -1) \cup (-1, +\infty)\).
Step by step solution
01
Apply the Chain Rule to Find the Derivative
The derivative of the function \(f(x)=\ln (2 x+2)\) can be calculated using the chain rule, which states that the derivative of a composite function is the derivative of the outside function times the derivative of the inside function. The derivative of a logarithmic function \(\ln u\), where \(u\) is a function of \(x\), can be written as \(\frac{1}{u}\). Therefore, the derivative of the function is \(f^{\prime}(x) = \frac{1}{2x+2}\times\frac{d(2x+2)}{dx}.\)
02
Calculate the Derivative of the Inside Function
The inside function is \(2x+2\). Its derivative, calculated using the power rule, is \(\frac{d(2x+2)}{dx}=2\). Substituting this in the previous equation gives \(f^{\prime}(x) = \frac{1}{2x+2}\times 2\).
03
Simplify the Derivative
After simplifying, the derivative of the function becomes \(f^{\prime}(x) = \frac{2}{2x+2} = \frac{1}{x+1}.\)
04
Find the Domain of the Derivative
The derivative is defined when the denominator is not equal to zero. Thus we set \(x+1 \neq 0\), giving \(x \neq -1\). Therefore, the domain of the derivative is \(-\infty<x<-1\) and \(-1<x<\infty\), which is the same as \(x \in (-\infty, -1) \cup (-1, +\infty)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Chain Rule
The chain rule is a fundamental concept in calculus, particularly when dealing with composite functions. Composite functions can be tricky because they involve a function nested inside another. To handle these, the chain rule tells us how to take derivatives effectively.
- The chain rule states that to find the derivative of a composite function \(g(f(x))\), you need to multiply the derivative of the outer function \(g\) evaluated at the inner function \(f\), by the derivative of the inner function \(f(x)\).
- In our exercise, the function is \(f(x) = \ln(2x + 2)\), where \(\ln(x)\) is the outer function and \(2x + 2\) is the inner function.
- The derivative of \(\ln(u)\) is \(\frac{1}{u}\). So, applying the chain rule involves multiplying \(\frac{1}{2x + 2}\) by the derivative of the inner function \(2x + 2\), which is 2.
Delving into Logarithmic Functions
Logarithmic functions are the inverse of exponential functions, and they play a key role when handling growth and decay problems in various fields.
- One of the most common logarithmic functions you will encounter in calculus is the natural logarithm, denoted as \(\ln(x)\), which is the inverse of the exponential function \(e^x\).
- The derivative of the natural logarithm \(\ln(x)\) is quite simple: it's \(\frac{1}{x}\). This property is integral when using the chain rule, as seen in the context of our exercise: \(f(x) = \ln(2x + 2)\).
Exploring the Domain of a Function
The domain of a function is essentially the set of all possible inputs (or \(x\)-values) for which the function is defined. Determining the domain is crucial, especially when evaluating functions involving logarithms or fractions, because certain inputs can make the function undefined.
- For our derivative \(f'(x) = \frac{1}{x+1}\), the function is undefined when the denominator equals zero.
- This means the function doesn’t exist where \(x + 1 = 0\), simplifying to \(x = -1\).