Find the sum of the first 8 terms for the following arithmetic sequence. a2 = 9, a4 = 19 The sum of the first 8 terms is

Calculus: Early Transcendentals
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ISBN:9781285741550
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:**

Find the sum of the first 8 terms for the following arithmetic sequence.

Given:
- \( a_2 = 9 \)
- \( a_4 = 19 \)

**Question:**
The sum of the first 8 terms is [ ].

**Explanation:**

To solve this problem, follow these steps:

1. **Identify the common difference**: 
   - Use the formula of the n-th term of an arithmetic sequence, which is \( a_n = a_1 + (n-1)d \).
   - Here, \( a_2 = 9 \) and \( a_4 = 19 \).
   - Set up the equations:
     - \( a_2 = a_1 + d = 9 \)
     - \( a_4 = a_1 + 3d = 19 \)
   - Solve these equations simultaneously to find \( a_1 \) and \( d \).

2. **Calculate the sum of the first 8 terms**:
   - The formula for the sum of the first n terms of an arithmetic sequence is:
     \[
     S_n = \frac{n}{2} \times (2a_1 + (n-1)d)
     \]
   - Substitute \( n = 8 \), along with the values for \( a_1 \) and \( d \), to find \( S_8 \).

This approach will yield the required sum for the first 8 terms of the sequence.
Transcribed Image Text:**Problem Statement:** Find the sum of the first 8 terms for the following arithmetic sequence. Given: - \( a_2 = 9 \) - \( a_4 = 19 \) **Question:** The sum of the first 8 terms is [ ]. **Explanation:** To solve this problem, follow these steps: 1. **Identify the common difference**: - Use the formula of the n-th term of an arithmetic sequence, which is \( a_n = a_1 + (n-1)d \). - Here, \( a_2 = 9 \) and \( a_4 = 19 \). - Set up the equations: - \( a_2 = a_1 + d = 9 \) - \( a_4 = a_1 + 3d = 19 \) - Solve these equations simultaneously to find \( a_1 \) and \( d \). 2. **Calculate the sum of the first 8 terms**: - The formula for the sum of the first n terms of an arithmetic sequence is: \[ S_n = \frac{n}{2} \times (2a_1 + (n-1)d) \] - Substitute \( n = 8 \), along with the values for \( a_1 \) and \( d \), to find \( S_8 \). This approach will yield the required sum for the first 8 terms of the sequence.
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