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Ch. 2 - Limits and Continuity
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 2, Problem 2.2.7

Suppose that a function f(x) is defined for all real values of x except x=c. Can anything be said about the existence of limx→c f(x)? Give reasons for your answer.

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Step 1: Understand the concept of a limit. The limit of a function f(x) as x approaches a value c, denoted as limx→c f(x), is the value that f(x) gets closer to as x gets closer to c.
Step 2: Consider the definition of a limit. A limit exists if the function approaches the same value from both the left and the right as x approaches c. This means that both the left-hand limit and the right-hand limit must be equal.
Step 3: Analyze the given condition. The function f(x) is defined for all real values of x except x=c. This means f(x) is not defined at x=c, but it can still be defined in intervals around c.
Step 4: Evaluate the possibility of the limit existing. Even though f(x) is not defined at x=c, the limit can still exist if the values of f(x) approach the same number from both sides of c.
Step 5: Conclude based on the analysis. The existence of limx→c f(x) depends on the behavior of f(x) as x approaches c from both sides. If the function approaches the same value from both sides, the limit exists; otherwise, it does not.

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Key Concepts

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

Limit of a Function

The limit of a function describes the behavior of the function as the input approaches a certain value. Specifically, limx→c f(x) examines the values that f(x) approaches as x gets arbitrarily close to c, regardless of whether f(c) is defined. Understanding limits is crucial for analyzing continuity and the behavior of functions near points of discontinuity.
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Continuity

A function is continuous at a point if the limit of the function as it approaches that point equals the function's value at that point. If f(x) is not defined at x=c, the function cannot be continuous at that point. However, limits can still exist, indicating that the function approaches a specific value as x approaches c, even if f(c) is undefined.
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One-Sided Limits

One-sided limits consider the behavior of a function as it approaches a point from one direction, either from the left (limx→c-) or from the right (limx→c+). If both one-sided limits exist and are equal, the overall limit limx→c f(x) exists. This concept is particularly relevant when analyzing functions that are undefined at a point, as it helps determine the limit's existence based on the function's behavior around that point.
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