In Exercises 55–60, express each sum using summation notation. Use a lower limit of summation of your choice and k for the index of summation.
Ch. 8 - Sequences, Induction, and Probability

Chapter 9, Problem 61
In Exercises 61–68, use the graphs of and to find each indicated sum.

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Identify the values of the sequence \( a_n \) from the graph for \( n = 1 \) to \( n = 5 \). From the graph, the points are: \( a_1 = -2 \), \( a_2 = 0 \), \( a_3 = 2 \), \( a_4 = 4 \), and \( a_5 = 6 \).
Write the expression for the sum you need to find: \( \sum_{i=1}^5 (a_i^2 + 1) \). This means for each \( i \) from 1 to 5, you square the value of \( a_i \), then add 1, and finally sum all these results.
Calculate each term inside the sum separately: For each \( i \), compute \( a_i^2 + 1 \). For example, for \( i=1 \), calculate \( (-2)^2 + 1 \), for \( i=2 \), calculate \( 0^2 + 1 \), and so on.
After finding each term \( a_i^2 + 1 \), add all these values together to get the total sum.
Write the final sum as \( (a_1^2 + 1) + (a_2^2 + 1) + (a_3^2 + 1) + (a_4^2 + 1) + (a_5^2 + 1) \) and simplify if needed.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sequences and Terms
A sequence is an ordered list of numbers where each number is called a term, denoted as a_n. Understanding how to identify and interpret terms from a graph is essential, as each point corresponds to a term's value at a specific position n.
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Introduction to Sequences
Summation Notation (Sigma Notation)
Summation notation, represented by the Greek letter Σ, is a concise way to express the sum of a sequence of terms. It includes an index of summation, lower and upper limits, and the general term to be summed, allowing efficient calculation of sums like Σ from i=1 to 5.
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Evaluating Expressions Involving Sequence Terms
To find sums involving expressions like (a_i^2 + 1), you must first determine each term a_i from the graph, then square it, add 1, and finally sum all these values over the given range. This process combines understanding of sequences, algebraic operations, and summation.
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