College Algebra (MindTap Course List)
12th Edition
ISBN:9781305652231
Author:R. David Gustafson, Jeff Hughes
Publisher:R. David Gustafson, Jeff Hughes
Chapter5: Exponential And Logarithmic Functions
Section5.3: Logarithmic Functions And Their Graphs
Problem 132E
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Which derivative of f do we use to test for concavity? How do we find inflection points?
![The given mathematical function is:
\[ f(x) = \ln (x^2 + 2x + 5) \]
This function represents the natural logarithm of the quadratic expression \(x^2 + 2x + 5\). In calculus and algebra, natural logarithms (logarithms to the base \(e\), where \(e \approx 2.718\)) are often used to simplify complex equations and model exponential growth or decay.
### Breaking Down the Equation:
- **\( \ln \)**: The natural logarithm function.
- **\( x^2 + 2x + 5 \)**: A quadratic expression.
### Key Points for Understanding:
1. **Natural Logarithm (ln)**:
- The natural logarithm function \( \ln(x) \) is the inverse of the exponential function \(e^x\).
- It is defined for all real numbers greater than zero.
- The natural logarithm of a number is the exponent to which \(e\) must be raised to equal that number.
2. **Quadratic Expression**:
- The expression inside the logarithm is a quadratic polynomial of the form \(ax^2 + bx + c\) where \(a = 1\), \(b = 2\), and \(c = 5\).
### Understanding the Function's Behavior:
- The function \(f(x)\) is defined for all real numbers \(x\) since \(x^2 + 2x + 5 > 0\) for all \(x \in \mathbb{R}\). This ensures that the argument of the natural logarithm is always positive, and hence \( \ln(x^2 + 2x + 5) \) is always defined.
### Example Calculations:
If we substitute specific values of \(x\) into \(f(x)\):
- For \(x = 0\):
\[ f(0) = \ln (0^2 + 2 \cdot 0 + 5) = \ln (5) \]
- For \(x = 1\):
\[ f(1) = \ln (1^2 + 2 \cdot 1 + 5) = \ln (8) \]
This function provides a way to measure the logarithmic growth subject to the quadratic expression inside the logarithm.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F08a51670-5bf9-44d1-ad0c-251791c78189%2Ff7b6fff1-db3c-46de-a175-18cde8a4f9b5%2F3s72mp_processed.png&w=3840&q=75)
Transcribed Image Text:The given mathematical function is:
\[ f(x) = \ln (x^2 + 2x + 5) \]
This function represents the natural logarithm of the quadratic expression \(x^2 + 2x + 5\). In calculus and algebra, natural logarithms (logarithms to the base \(e\), where \(e \approx 2.718\)) are often used to simplify complex equations and model exponential growth or decay.
### Breaking Down the Equation:
- **\( \ln \)**: The natural logarithm function.
- **\( x^2 + 2x + 5 \)**: A quadratic expression.
### Key Points for Understanding:
1. **Natural Logarithm (ln)**:
- The natural logarithm function \( \ln(x) \) is the inverse of the exponential function \(e^x\).
- It is defined for all real numbers greater than zero.
- The natural logarithm of a number is the exponent to which \(e\) must be raised to equal that number.
2. **Quadratic Expression**:
- The expression inside the logarithm is a quadratic polynomial of the form \(ax^2 + bx + c\) where \(a = 1\), \(b = 2\), and \(c = 5\).
### Understanding the Function's Behavior:
- The function \(f(x)\) is defined for all real numbers \(x\) since \(x^2 + 2x + 5 > 0\) for all \(x \in \mathbb{R}\). This ensures that the argument of the natural logarithm is always positive, and hence \( \ln(x^2 + 2x + 5) \) is always defined.
### Example Calculations:
If we substitute specific values of \(x\) into \(f(x)\):
- For \(x = 0\):
\[ f(0) = \ln (0^2 + 2 \cdot 0 + 5) = \ln (5) \]
- For \(x = 1\):
\[ f(1) = \ln (1^2 + 2 \cdot 1 + 5) = \ln (8) \]
This function provides a way to measure the logarithmic growth subject to the quadratic expression inside the logarithm.
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