Find the average value of the function f over the interval [0, 15]. 4 f(x) = x + 1

College Algebra
7th Edition
ISBN:9781305115545
Author:James Stewart, Lothar Redlin, Saleem Watson
Publisher:James Stewart, Lothar Redlin, Saleem Watson
Chapter2: Functions
Section: Chapter Questions
Problem 20P: In these problem you are asked to find a function that models a real-life situation and then use the...
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### Calculating the Average Value of a Function

**Problem Statement:**
Find the average value of the function \( f \) over the interval \([0, 15]\).

The function \( f(x) \) is defined as:
\[ f(x) = \frac{4}{x + 1} \]

**Step-by-Step Solution:**

1. **Understand the Formula:**
   The average value of a function \( f(x) \) over the interval \([a, b]\) is given by:
   \[
   \text{Average value} = \frac{1}{b - a} \int_{a}^{b} f(x) \, dx
   \]
   
2. **Substitute the Given Values:**
   Here \( a = 0 \) and \( b = 15 \). Substitute these into the formula:
   \[
   \text{Average value} = \frac{1}{15 - 0} \int_{0}^{15} \frac{4}{x + 1} \, dx
   \]
   Simplifying the constant term, we get:
   \[
   \text{Average value} = \frac{1}{15} \int_{0}^{15} \frac{4}{x + 1} \, dx
   \]

3. **Compute the Integral:**
   To compute the integral, use the substitution method. Let \( u = x + 1 \) hence \( du = dx \).
   
   When \( x = 0 \), \( u = 1 \).
   
   When \( x = 15 \), \( u = 16 \).
   
   Rewriting the integral in terms of \( u \):
   \[
   \int_{0}^{15} \frac{4}{x + 1} \, dx = \int_{1}^{16} \frac{4}{u} \, du
   \]
   
   The integral of \( \frac{4}{u} \) is \( 4 \ln|u| \):
   \[
   \int_{1}^{16} \frac{4}{u} \, du = 4 \ln|u| \Big|_{1}^{16}
   \]
   
4. **Evaluate the Antiderivative:**
   Substituting the limits into the antiderivative:
   \[
   4
Transcribed Image Text:### Calculating the Average Value of a Function **Problem Statement:** Find the average value of the function \( f \) over the interval \([0, 15]\). The function \( f(x) \) is defined as: \[ f(x) = \frac{4}{x + 1} \] **Step-by-Step Solution:** 1. **Understand the Formula:** The average value of a function \( f(x) \) over the interval \([a, b]\) is given by: \[ \text{Average value} = \frac{1}{b - a} \int_{a}^{b} f(x) \, dx \] 2. **Substitute the Given Values:** Here \( a = 0 \) and \( b = 15 \). Substitute these into the formula: \[ \text{Average value} = \frac{1}{15 - 0} \int_{0}^{15} \frac{4}{x + 1} \, dx \] Simplifying the constant term, we get: \[ \text{Average value} = \frac{1}{15} \int_{0}^{15} \frac{4}{x + 1} \, dx \] 3. **Compute the Integral:** To compute the integral, use the substitution method. Let \( u = x + 1 \) hence \( du = dx \). When \( x = 0 \), \( u = 1 \). When \( x = 15 \), \( u = 16 \). Rewriting the integral in terms of \( u \): \[ \int_{0}^{15} \frac{4}{x + 1} \, dx = \int_{1}^{16} \frac{4}{u} \, du \] The integral of \( \frac{4}{u} \) is \( 4 \ln|u| \): \[ \int_{1}^{16} \frac{4}{u} \, du = 4 \ln|u| \Big|_{1}^{16} \] 4. **Evaluate the Antiderivative:** Substituting the limits into the antiderivative: \[ 4
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