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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 45c

Analyze the following limits and find the vertical asymptotes of f(x) =(x − 5) / (x2 − 25).
lim x→−5+ f(x)

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1
Step 1: Identify the points where the function f(x) = \( \frac{x - 5}{x^2 - 25} \) is undefined. This occurs when the denominator is zero. Set the denominator equal to zero: \( x^2 - 25 = 0 \).
Step 2: Solve the equation \( x^2 - 25 = 0 \) to find the values of x that make the denominator zero. This can be factored as \( (x - 5)(x + 5) = 0 \), giving the solutions \( x = 5 \) and \( x = -5 \).
Step 3: Determine if these points are vertical asymptotes by checking the behavior of the function as x approaches these values. Since the numerator \( x - 5 \) is zero at \( x = 5 \), the function has a removable discontinuity at \( x = 5 \), not a vertical asymptote.
Step 4: Analyze the limit \( \lim_{x \to -5^+} f(x) \). As x approaches -5 from the right, the denominator \( x^2 - 25 \) approaches zero, and the numerator \( x - 5 \) approaches -10. This indicates a vertical asymptote at \( x = -5 \).
Step 5: Conclude that the function has a vertical asymptote at \( x = -5 \) because the limit of f(x) as x approaches -5 from the right is either positive or negative infinity.

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Key Concepts

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

Limits

Limits describe the behavior of a function as the input approaches a certain value. In this context, evaluating the limit as x approaches -5 from the right (denoted as x→−5⁺) helps determine how the function behaves near that point, which is crucial for identifying vertical asymptotes.
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Vertical Asymptotes

Vertical asymptotes occur at values of x where a function approaches infinity or negative infinity, typically where the denominator of a rational function equals zero while the numerator does not. For the function f(x) = (x − 5) / (x² − 25), finding the points where the denominator is zero will help identify potential vertical asymptotes.
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Factoring Polynomials

Factoring polynomials is a method used to simplify expressions and find roots. In this case, the denominator x² − 25 can be factored into (x − 5)(x + 5), which reveals the points where the function may have vertical asymptotes, specifically at x = 5 and x = -5.
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