S(1) = In (r² + 2x +5)

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
Topic Video
Question

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.
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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