Chapter 1: Problem 12
Approximate the given limits both numerically and graphically. $$ \lim _{x \rightarrow 2} \frac{x^{2}+7 x+10}{x^{2}-4 x+4} $$
Short Answer
Expert verified
The limit does not exist due to a vertical asymptote at \( x=2 \).
Step by step solution
01
Analyze the Expression
Given the limit \( \lim _{x \rightarrow 2} \frac{x^{2}+7 x+10}{x^{2}-4 x+4} \), we need to determine if the expression is undefined at \( x=2 \). Calculate \( x^2 - 4x + 4 \) when \( x=2 \).\[ (2)^2 - 4 imes 2 + 4 = 4 - 8 + 4 = 0 \] This results in a division by zero, indicating a possible indeterminate form.
02
Simplify the Expression
Factor the numerator and the denominator to simplify the expression. The numerator \( x^2 + 7x + 10 \) can be factored as \((x+5)(x+2)\). The denominator \( x^2 - 4x + 4 \) can be factored as \((x-2)^2\). So the expression becomes:\[ \frac{(x+5)(x+2)}{(x-2)^2} \].
03
Determine the Behavior near x=2
Since \( (x-2) \) appears twice in the denominator, and is not a factor of the numerator, the function has a vertical asymptote at \( x = 2 \). This usually indicates that the limit does not exist numerically.
04
Graphical Analysis
Plot the function \( y = \frac{x^2 + 7x + 10}{x^2 - 4x + 4} \) to observe its behavior around \( x=2 \). The graph will show a vertical asymptote at \( x=2 \), confirming the indication from our simplification that the function diverges.
05
Conclusion
Since both graphical analysis and algebraic manipulation demonstrate that the function diverges at \( x=2 \) (because of the vertical asymptote), the limit does not exist.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Indeterminate Forms
When dealing with limits, especially as a variable approaches a value that causes a division by zero, we encounter what are known as **indeterminate forms**. In calculus, indeterminate forms often require additional analysis to determine the limit's value, or to conclude if a limit exists at all. In the given exercise, when we substitute \( x = 2 \) in the denominator, the expression results in zero, suggesting an indeterminate form of the type \( \frac{0}{0} \). This indicates that at least one part of the equation needs to be simplified or re-evaluated to determine a limit that can be analyzed meaningfully. When you see such forms, remember they denote that the limit could be anything: finite, infinite, or might not exist. The presence of this form is a signpost that further work is necessary to reveal the nature of the limit.
- Helpful techniques include algebraic simplification, L'Hôpital's rule, or converting the expression into a different form.
- In this problem, simplification helped understand the behavior of the function around the point of interest.
Simplifying Algebraic Expressions
Simplification of algebraic expressions is a crucial step in limit problems, especially when faced with indeterminate forms. Simplifying involves manipulating the expression into a more manageable form, often by factoring or canceling common terms. In this exercise, the numerator \( x^2 + 7x + 10 \) is factored to \((x+5)(x+2)\), and the denominator \( x^2 - 4x + 4 \) is factored to \((x-2)^2\).
By simplifying the expression, we gain insights into how the function behaves near \( x=2 \).
By simplifying the expression, we gain insights into how the function behaves near \( x=2 \).
- Factoring helps identify terms that contribute to zero in the numerator and denominator.
- Cancel common factors only if they appear in both the numerator and denominator to simplify the expression.
Graphical Analysis of Functions
Graphical analysis provides a visual understanding of how a function behaves, especially useful in cases of indeterminate forms or undefined points. By plotting the graph of the function\( y = \frac{x^2 + 7x + 10}{x^2 - 4x + 4} \), one can visually discern changes at critical points, such as \( x = 2 \). The graph in this exercise shows a distinct vertical line known as a vertical asymptote at \( x=2 \).
This reflects the nature of the limit analyzed algebraically, confirming the analytical deduction that the function diverges as \( x \) approaches 2.
This reflects the nature of the limit analyzed algebraically, confirming the analytical deduction that the function diverges as \( x \) approaches 2.
- Asymptotes are lines that the function's graph approaches but never touches.
- Observe how the function trends around points of interest to verify analytical findings.