/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 7 The terms of a sequence of parti... [FREE SOLUTION] | 91Ó°ÊÓ

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The terms of a sequence of partial sums are defined by \(S_{n}=\sum_{k=1}^{n} k^{2}\) for \(n=1,2,3, \ldots .\) Evaluate the first four terms of the sequence.

Short Answer

Expert verified
Answer: The first four terms of the sequence of partial sums are \(S_1 = 1\), \(S_2 = 5\), \(S_3 = 14\), and \(S_4 = 30\).

Step by step solution

01

Find \(S_1\) (the first term)

Plug in \(n = 1\) into the expression for the sequence of partial sums: $$S_1 = \sum_{k=1}^{1} k^2 = 1^2 = 1.$$ So, the first term of the sequence is \(S_1 = 1\).
02

Find \(S_2\) (the second term)

Plug in \(n = 2\) into the expression for the sequence of partial sums: $$S_2 = \sum_{k=1}^{2} k^2 = 1^2 + 2^2 = 1 + 4 = 5.$$ So, the second term of the sequence is \(S_2 = 5\).
03

Find \(S_3\) (the third term)

Plug in \(n = 3\) into the expression for the sequence of partial sums: $$S_3 = \sum_{k=1}^{3} k^2 = 1^2 + 2^2 + 3^2 = 1 + 4 + 9 = 14.$$ So, the third term of the sequence is \(S_3 = 14\).
04

Find \(S_4\) (the fourth term)

Plug in \(n = 4\) into the expression for the sequence of partial sums: $$S_4 = \sum_{k=1}^{4} k^2 = 1^2 + 2^2 + 3^2 + 4^2 = 1 + 4 + 9 + 16 = 30.$$ So, the fourth term of the sequence is \(S_4 = 30\). In summary, the first four terms of the sequence of partial sums are \(S_1 = 1\), \(S_2 = 5\), \(S_3 = 14\), and \(S_4 = 30\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Series and Sequences
A sequence is essentially a list of numbers arranged in a specific order. Each number in a sequence is called a 'term'. Sequences can be finite, with a specific number of terms, or infinite, continuing indefinitely.
One common type of sequence is an arithmetic sequence, where each term is obtained by adding a fixed number to the previous term. Another type is a geometric sequence, where each term is found by multiplying the previous one by a constant.
In the case of this exercise, we are examining a sequence of partial sums. A partial sum is the sum of a specified number of terms from a sequence. For example, if you have a sequence of numbers and you add up the first, second, and third terms, you get a partial sum.
Understanding the behavior and properties of sequences, such as their growth rate or the pattern in their terms, is essential in many areas of mathematics and its applications.
Summation Notation
Summation notation, represented by the Greek letter sigma (\(\Sigma\), is a concise way to represent the addition of a sequence of numbers. It's particularly useful for adding a large number of terms compactly and clearly.
The general form of summation notation is: \[\sum_{k=m}^{n} a_k\] where \(a_k\) is a term in the sequence, \(k\) is the index of summation that runs from \(m\) to \(n\). This tells you to sum all terms \(a_k\) starting at index \(k=m\) and ending at index \(k=n\).
In this exercise, the summation notation \(\sum_{k=1}^{n} k^2\) instructs us to add the squares of all integers from \(1\) to \(n\). This convenient notation is a vital skill in mathematics because it simplifies expression manipulation and understanding of series-related problems.
Squares of Integers
The square of an integer is the integer multiplied by itself. For example, the square of 3 is \(3^2 = 9\). Squares of integers show up frequently in various mathematical contexts, including geometry, algebra, and number theory.
When you square an integer, the result is always a positive number, or zero if squaring zero. This property can help in recognizing number patterns and solving equations.
In this exercise, each term in the sequence of partial sums is derived from the sum of squares. For example, for \(n = 3\), we compute \(1^2 + 2^2 + 3^2 = 14\). Squaring each term and then summing results is what leads us to the values of the partial sum sequence, such as \(S_3 = 14\). Recognizing the role of squares helps in understanding the mechanics behind growing sequences of sums.

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Most popular questions from this chapter

$$\text {Evaluate each series or state that it diverges.}$$ $$\sum_{k=1}^{\infty} \frac{\pi^{k}}{e^{k+1}}$$

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It can be proved that if a series converges absolutely, then its terms may be summed in any order without changing the value of the series. However, if a series converges conditionally, then the value of the series depends on the order of summation. For example, the (conditionally convergent) alternating harmonic series has the value $$ 1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+\dots=\ln 2 $$ Show that by rearranging the terms (so the sign pattern is \(++-\) ), $$ 1+\frac{1}{3}-\frac{1}{2}+\frac{1}{5}+\frac{1}{7}-\frac{1}{4}+\cdots=\frac{3}{2} \ln 2 $$

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