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Ch. 8 - Sequences, Induction, and Probability
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 9, Problem 43

Express each sum using summation notation. Use 1 as the lower limit of summation and i for the index of summation. 12+22+32++1521^2+2^2+3^2+⋯+ 15^2

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Identify the pattern in the sum: the terms are squares of consecutive integers starting from 1 up to 15, i.e., 1^2, 2^2, 3^2, ..., 15^2.
Recognize that the index of summation, denoted by \( i \), will represent each integer in the sequence from 1 to 15.
Write the general term of the sum using the index \( i \), which is \( i^2 \) since each term is the square of \( i \).
Set the lower limit of summation to 1, as specified, and the upper limit to 15, the last term in the sum.
Express the entire sum in summation notation as: \[ \sum_{i=1}^{15} i^2 \]

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Summation Notation

Summation notation is a concise way to represent the sum of a sequence of terms using the sigma symbol (∑). It includes an index of summation, lower and upper limits, and the general term to be summed. For example, ∑ from i=1 to n of a_i represents the sum a_1 + a_2 + ... + a_n.
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Index of Summation

The index of summation is a variable, often i, that represents each term's position in the sequence being summed. It starts at the lower limit and increments by 1 until it reaches the upper limit. This index helps define the general term in the summation expression.
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Expressing Sums of Powers

When summing powers of integers, such as squares, the general term is written as i raised to the power, e.g., i^2. Expressing sums like 1^2 + 2^2 + ... + 15^2 in summation notation involves writing ∑ from i=1 to 15 of i^2, which compactly represents the entire sum.
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