/*! 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 62 For the following infinite serie... [FREE SOLUTION] | 91Ó°ÊÓ

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For the following infinite series, find the first four terms of the sequence of partial sums. Then make a conjecture about the value of the infinite series. $$1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\dots$$

Short Answer

Expert verified
Answer: The infinite geometric series converges to a sum of 2.

Step by step solution

01

Identify the infinite series

The given series is an infinite geometric series with the first term, a, equal to 1, and the common ratio, r, equal to 1/2. The series can be represented as: $$\sum_{n=0}^{\infty} a \cdot r^n$$, which in this case is: $$\sum_{n=0}^{\infty} 1 \cdot \left(\frac{1}{2}\right)^n$$
02

Calculate the first partial sum

To find the first partial sum, S1, add the first term of the series: $$S_1 = 1$$
03

Calculate the second partial sum

To find the second partial sum, S2, add the first and second terms of the series: $$S_2 = 1 + \frac{1}{2} = \frac{3}{2}$$
04

Calculate the third partial sum

To find the third partial sum, S3, add the first, second, and third terms of the series: $$S_3 = 1 + \frac{1}{2} + \frac{1}{4} = \frac{7}{4}$$
05

Calculate the fourth partial sum

To find the fourth partial sum, S4, add the first, second, third, and fourth terms of the series: $$S_4 = 1 + \frac{1}{2} + \frac{1}{4} + \frac{1}{8} = \frac{15}{8}$$
06

Make a conjecture about the value of the infinite series

To make a conjecture about the value of the infinite series, observe the pattern of the partial sums. We can see that the partial sums are getting closer to a specific value: $$1, \frac{3}{2}, \frac{7}{4}, \frac{15}{8}, \dots$$ The denominators are increasing powers of 2 and the numerators are 1 less than the next power of 2. This suggests that the infinite series converges to a value close to but less than 2. In fact, it converges to 2 as the partial sums become: $$1, \frac{3}{2}, \frac{7}{4}, \frac{15}{8}, \dots$$ which can be rewritten as: $$\frac{2}{2},\frac{4}{2},\frac{8}{4},\frac{16}{8},\dots$$ The numerators are increasing powers of 2 (excluding the first term), and the denominators are powers of 2 as well. As the value of n approaches infinity, the difference between the numerator and denominator in each fraction converges to 0, thus the series converges to 2. Therefore, we can conjecture that the infinite series converges to a sum of 2.

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Most popular questions from this chapter

Convergence parameter Find the values of the parameter \(p>0\) for which the following series converge. $$\sum_{k=2}^{\infty} \frac{1}{(\ln k)^{p}}$$

Consider the geometric series $$S=\sum_{k=0}^{\infty} r^{k}$$ which has the value \(1 /(1-r)\) provided \(|r|<1 .\) Let \(S_{n}=\sum_{k=0}^{n-1} r^{k}=\frac{1-r^{n}}{1-r}\) be the sum of the first \(n\) terms. The remainder \(R_{n}\) is the error in approximating \(S\) by \(S_{n} .\) Show that $$R_{n}=\left|S-S_{n}\right|=\left|\frac{r^{n}}{1-r}\right|$$

A well-known method for approximating \(\sqrt{c}\) for positive real numbers \(c\) consists of the following recurrence relation (based on Newton's method). Let \(a_{0}=c\) and $$a_{n+1}=\frac{1}{2}\left(a_{n}+\frac{c}{a_{n}}\right), \quad \text { for } n=0,1,2,3, \dots$$ a. Use this recurrence relation to approximate \(\sqrt{10} .\) How many terms of the sequence are needed to approximate \(\sqrt{10}\) with an error less than \(0.01 ?\) How many terms of the sequence are needed to approximate \(\sqrt{10}\) with an error less than \(0.0001 ?\) (To compute the error, assume a calculator gives the exact value.) b. Use this recurrence relation to approximate \(\sqrt{c},\) for \(c=2\) \(3, \ldots, 10 .\) Make a table showing how many terms of the sequence are needed to approximate \(\sqrt{c}\) with an error less than \(0.01.\)

Use Exercise 89 to determine how many terms of each series are needed so that the partial sum is within \(10^{-6}\) of the value of the series (that is, to ensure \(R_{n}<10^{-6}\) ). a. \(\sum_{k=0}^{\infty} 0.72^{k}\) b. \(\sum_{k=0}^{\infty}(-0.25)^{k}\)

a. Consider the number 0.555555...., which can be viewed as the series \(5 \sum_{k=1}^{\infty} 10^{-k} .\) Evaluate the geometric series to obtain a rational value of \(0.555555 \ldots\) b. Consider the number \(0.54545454 \ldots,\) which can be represented by the series \(54 \sum_{k=1}^{\infty} 10^{-2 k} .\) Evaluate the geometric series to obtain a rational value of the number. c. Now generalize parts (a) and (b). Suppose you are given a number with a decimal expansion that repeats in cycles of length \(p,\) say, \(n_{1}, n_{2} \ldots \ldots, n_{p},\) where \(n_{1}, \ldots, n_{p}\) are integers between 0 and \(9 .\) Explain how to use geometric series to obtain a rational form of the number. d. Try the method of part (c) on the number \(0.123456789123456789 \ldots\) e. Prove that \(0 . \overline{9}=1\)

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