15. Find the sum of 1 1.3 + 1 =+ 3.5 n = 1 1 + 5.7

Calculus: Early Transcendentals
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Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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**Problem Statement:**
15. Find the sum of 
\[ \frac{1}{1 \cdot 3} + \frac{1}{3 \cdot 5} + \frac{1}{5 \cdot 7} + \cdots \]

**Explanation:**
The given mathematical expression is an infinite series. The terms of this series are expressed in the form:

\[ \frac{1}{(2n-1)(2n+1)} \]

where \( n \) is a positive integer starting from 1.
So, the series can be written as:

\[ \sum_{n=1}^{\infty} \frac{1}{(2n-1)(2n+1)} \]

**Steps to Solve:**

1. **Express each term in a partial fraction form:**
   - We can rewrite the general term \(\frac{1}{(2n-1)(2n+1)}\) using partial fractions.

   \[ \frac{1}{(2n-1)(2n+1)} = \frac{A}{2n-1} + \frac{B}{2n+1} \]

   Solving for \( A \) and \( B \):
   
   \[ 1 = A(2n+1) + B(2n-1) \]
   
   Setting \[ n \to \infty \], it can be found that:
   
   \[ A = \frac{1}{2} \] and \[ B = -\frac{1}{2} \]
   
   So:
   
   \[ \frac{1}{(2n-1)(2n+1)} = \frac{1}{2} \left( \frac{1}{2n-1} - \frac{1}{2n+1} \right) \]

2. **Sum of the series:**
   - Substituting this back into the series:

   \[ \sum_{n=1}^{\infty} \frac{1}{2} \left( \frac{1}{2n-1} - \frac{1}{2n+1} \right) \]

   - This is a telescoping series, which means that most of the terms will cancel each other out.

   \[ \sum_{n=1}^{\infty} \
Transcribed Image Text:**Problem Statement:** 15. Find the sum of \[ \frac{1}{1 \cdot 3} + \frac{1}{3 \cdot 5} + \frac{1}{5 \cdot 7} + \cdots \] **Explanation:** The given mathematical expression is an infinite series. The terms of this series are expressed in the form: \[ \frac{1}{(2n-1)(2n+1)} \] where \( n \) is a positive integer starting from 1. So, the series can be written as: \[ \sum_{n=1}^{\infty} \frac{1}{(2n-1)(2n+1)} \] **Steps to Solve:** 1. **Express each term in a partial fraction form:** - We can rewrite the general term \(\frac{1}{(2n-1)(2n+1)}\) using partial fractions. \[ \frac{1}{(2n-1)(2n+1)} = \frac{A}{2n-1} + \frac{B}{2n+1} \] Solving for \( A \) and \( B \): \[ 1 = A(2n+1) + B(2n-1) \] Setting \[ n \to \infty \], it can be found that: \[ A = \frac{1}{2} \] and \[ B = -\frac{1}{2} \] So: \[ \frac{1}{(2n-1)(2n+1)} = \frac{1}{2} \left( \frac{1}{2n-1} - \frac{1}{2n+1} \right) \] 2. **Sum of the series:** - Substituting this back into the series: \[ \sum_{n=1}^{\infty} \frac{1}{2} \left( \frac{1}{2n-1} - \frac{1}{2n+1} \right) \] - This is a telescoping series, which means that most of the terms will cancel each other out. \[ \sum_{n=1}^{\infty} \
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