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Ch. 2 - Limits
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 2, Problem 2.91

A sequence is an infinite, ordered list of numbers that is often defined by a function. For example, the sequence {2,4,6,8,…} is specified by the function f(n) = 2n, where n=1,2,3,….The limit of such a sequence is lim n→∞ f(n), provided the limit exists. All the limit laws for limits at infinity may be applied to limits of sequences. Find the limit of the following sequences or state that the limit does not exist. 


{2,3/4,4/9,5/16,…}, which is defined by f(n) = (n+1) / n^2, for n=1,2,3,…

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1
Identify the sequence function: f(n) = \(\frac{n+1}{n^2}\).
Consider the limit of the sequence as n approaches infinity: \(\lim\)_{n \(\to\) \(\infty\)} \(\frac{n+1}{n^2}\).
Simplify the expression by dividing the numerator and the denominator by n^2: \(\lim\)_{n \(\to\) \(\infty\)} \(\frac{\frac{n+1}{n^2}\)}{\(\frac{n^2}{n^2}\)} = \(\lim\)_{n \(\to\) \(\infty\)} \(\frac{\frac{1}{n}\) + \(\frac{1}{n^2}\)}{1}.
As n approaches infinity, both \(\frac{1}{n}\) and \(\frac{1}{n^2}\) approach 0.
Conclude that the limit of the sequence is 0.

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Key Concepts

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

Sequences

A sequence is an ordered list of numbers that can be defined by a specific function. Each term in the sequence corresponds to a natural number, and the sequence can be finite or infinite. Understanding sequences is crucial for analyzing their behavior, particularly as the index approaches infinity.

Limits

The limit of a sequence describes the value that the terms of the sequence approach as the index goes to infinity. It is denoted as lim n→∞ f(n) and is fundamental in calculus for determining the behavior of sequences. If the limit exists, it provides insight into the long-term behavior of the sequence.
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Limit Laws

Limit laws are rules that govern the evaluation of limits, particularly at infinity. These laws allow for the manipulation of limits in various forms, such as sums, products, and quotients of functions. Applying these laws correctly is essential for finding the limits of sequences and ensuring accurate results.
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Related Practice
Textbook Question

Use the precise definition of a limit to prove the following limits. Specify a relationship between ε and δ that guarantees the limit exists.

lim x→1 x^4=1

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If a function f represents a system that varies in time, the existence of lim limtf(t){\(\displaystyle\[\lim\)_{t\(\rightarrow\]\infty\)}{f(t)}} means that the system reaches a steady state (or equilibrium). For the following systems, determine whether a steady state exists and give the steady-state value.


The population of a bacteria culture is given by p(t)=2500t+1p\(\left\)(t\(\right\))=\(\frac{2500}{t+1}\).

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Use a graph of f to estimate limxaf(x){\(\displaystyle\]\lim\)_{x\(\to\) a}}f\(\left\)(x\(\right\)) or to show that the limit does not exist. Evaluate f(x) near x=ax=a to support your conjecture.

f(x)=1cos(2x2)(x1)2;a=1f\(\left\)(x\(\right\))=\(\frac{1-\cos\left(2x-2\right)}{\left(x-1\right)^2}\);a=1

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Determine the points on the interval (0, 5) at which the following functions f have discontinuities. At each point of discontinuity, state the conditions in the continuity checklist that are violated. <IMAGE>

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Determine limxf(x)\(\lim\)_{x\(\rightarrow\]\infty\)}f\(\left\)(x\(\right\)) and limxf(x)\(\lim\)_{x\(\rightarrow\)-\(\infty\)}f\(\left\)(x\(\right\)) for the following functions. Then give the horizontal asymptotes of ff (if any).


f(x)=4x3+12x3+16x6+1f\(\left\)(x\(\right\))=\(\frac{4x^3+1}{2x^3+\sqrt{16x^6+1}\)}

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Find all vertical asymptotes x=ax=a of the following functions. For each value of aa, determine limxa+f(x){\(\displaystyle\]\lim\)_{x\(\to\) a^{+}}}f\(\left\)(x\(\right\)), limxaf(x){\(\displaystyle\]\lim\)_{x\(\to\) a^{-}}}f\(\left\)(x\(\right\)), and limxaf(x){\(\displaystyle\]\lim\)_{x\(\to\) a}}f\(\left\)(x\(\right\)).

f(x)=cos(x)x2+2xf\(\left\)(x\(\right\))=\(\frac{\cos\left(x\right)}{x^2+2x}\)