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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 2.76b

Find the vertical asymptotes. For each vertical asymptote x=a, analyze lim x→a- f(x) and lim x→a+ f(x).
f(x) = (x^4−1)/(x^2−1)

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To find the vertical asymptotes, set the denominator equal to zero: \(x^2 - 1 = 0\). Solve for \(x\) to find the points where the function is undefined.
This can be factored as \((x - 1)(x + 1) = 0\). Therefore, the solutions are \(x = 1\) and \(x = -1\). These are the potential vertical asymptotes.
Check if the numerator \(x^4 - 1\) can be factored to cancel any common factors with the denominator. Factor \(x^4 - 1\) as \((x^2 - 1)(x^2 + 1)\).
The expression becomes \(\frac{(x^2 - 1)(x^2 + 1)}{x^2 - 1}\). Cancel the common factor \(x^2 - 1\), leaving \(f(x) = x^2 + 1\) for \(x \neq \pm 1\).
For \(x = 1\) and \(x = -1\), analyze \(\lim_{x \to 1^-} f(x)\), \(\lim_{x \to 1^+} f(x)\), \(\lim_{x \to -1^-} f(x)\), and \(\lim_{x \to -1^+} f(x)\) using the simplified function \(f(x) = x^2 + 1\).

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Key Concepts

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

Vertical Asymptotes

Vertical asymptotes occur in a function when the output approaches infinity as the input approaches a certain value from either the left or the right. This typically happens at points where the function is undefined, often due to division by zero. Identifying vertical asymptotes involves finding the values of x that make the denominator zero while ensuring the numerator is not also zero at those points.
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Limits

Limits are fundamental in calculus, representing the value that a function approaches as the input approaches a certain point. In the context of vertical asymptotes, we analyze the left-hand limit (as x approaches a from the left) and the right-hand limit (as x approaches a from the right) to determine the behavior of the function near the asymptote. This helps in understanding whether the function tends to positive or negative infinity.
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Factoring Polynomials

Factoring polynomials is a technique used to simplify expressions, making it easier to analyze their behavior, such as finding asymptotes. In the given function f(x) = (x^4−1)/(x^2−1), factoring both the numerator and denominator can reveal common factors and help identify points of discontinuity. This process is crucial for determining where vertical asymptotes may exist and for simplifying the function before evaluating limits.
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Related Practice
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For any real number x, the floor function (or greatest integer function) ⌊x⌋ is the greatest integer less than or equal to x (see figure).


a. Compute lim x→−1^− ⌊x⌋, lim x→−1^+ ⌊x⌋,lim x→2^− ⌊x⌋, and lim x→2^+ ⌊x⌋.

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Determine whether the following statements are true and give an explanation or counterexample.


a. The graph of a function can never cross one of its horizontal asymptotes.

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Assume you invest \(250 at the end of each year for 10 years at an annual interest rate of rr. The amount of money in your account after 10 years is given by A(r)=250((1+r)101)rA\left(r\right)=\frac{250\left(\left(1+r\right)^{10}-1\right)}{r}. Assume your goal is to have \)3500 in your account after 10 years.


b. Use a calculator to estimate the interest rate required to reach your financial goal.

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Let g(x)={x2+xif x<1aif x=13x+5if x>1g\(\left\)(x\(\right\))=\(\begin{cases}\)x^2+x & \(\text{if }\)x<1\\ a & \(\text{if }\)x=1\\ 3x+5 & \(\text{if }\)x>1\(\end{cases}\)

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Complete the following steps for the given functions. 


b. Find the vertical asymptotes of f (if any).


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Textbook Question

Graph the function f(x)=e^−x / x(x+2)^2 using a graphing utility. (Experiment with your choice of a graphing window.) Use your graph to determine the following limits.


b. lim x→−2 f(x)

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