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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 2.87

Use an appropriate limit definition to prove the following limits.


lim x→ 5x^2 − 25 / x − 5=10

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1
Identify the limit expression: \( \lim_{{x \to 5}} \frac{{x^2 - 25}}{{x - 5}} \).
Recognize that the expression \( x^2 - 25 \) can be factored as \((x - 5)(x + 5)\).
Rewrite the limit expression using the factorization: \( \lim_{{x \to 5}} \frac{{(x - 5)(x + 5)}}{{x - 5}} \).
Cancel the common factor \((x - 5)\) in the numerator and denominator, simplifying the expression to \( \lim_{{x \to 5}} (x + 5) \).
Evaluate the limit by direct substitution: substitute \(x = 5\) into the simplified expression \(x + 5\).

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Key Concepts

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

Limit Definition

The limit definition in calculus refers to the formal approach to finding the limit of a function as it approaches a certain point. It involves evaluating the behavior of the function as the input values get arbitrarily close to a specified value, often denoted as 'a'. This concept is foundational for understanding continuity, derivatives, and integrals.
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Factoring Polynomials

Factoring polynomials is the process of breaking down a polynomial expression into simpler components, or factors, that can be multiplied together to yield the original polynomial. In the context of limits, factoring can help simplify expressions that yield indeterminate forms, such as 0/0, allowing for easier evaluation of the limit.
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Indeterminate Forms

Indeterminate forms occur in calculus when evaluating limits leads to expressions that do not provide clear information about the limit's value, such as 0/0 or ∞/∞. Recognizing these forms is crucial, as they often require additional techniques, like factoring or L'Hôpital's Rule, to resolve and find the actual limit.
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Related Practice
Textbook Question

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)=6x29x+83x2+2f\(\left\)(x\(\right\))=\(\frac{6x^2-9x+8}{3x^2+2}\)

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Textbook Question

Consider the position function s(t) =−16t^2+100t representing the position of an object moving vertically along a line. Sketch a graph of s with the secant line passing through (0.5, s(0.5)) and (2, s(2)). Determine the slope of the secant line and explain its relationship to the moving object.

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Textbook Question

Sketch a graph of f and use it to make a conjecture about the values of f(a), lim x→a^−f(x),lim x→a^+f(x), and lim x→a f(x) or state that they do not exist.

f(x) = x^2+x−2 / x−1; a=1

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Textbook Question

Use analytical methods and/or a graphing utility to identify the vertical asymptotes (if any) of the following functions.

f(x)=x^2−3x+2 / x^10−x^9

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Textbook Question

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. 


{0,1/2,2/3,3/4,…}, which is defined by f(n) = (n−1) / n, for n=1,2,3,…

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Textbook Question

Estimate the following limits using graphs or tables.

limh0ln(1+h)h{\(\displaystyle\]\lim\)_{h\(\to\)0}}\(\frac{\ln\left(1+h\right)}{h}\)

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