Chapter 2: Problem 39
Find the limits in Exercises \(37-48\) $$ \lim _{x \rightarrow 2^{-}} \frac{3}{x-2} $$
Short Answer
Expert verified
The limit is \(-\infty\).
Step by step solution
01
Understanding the Limit
The expression \( \lim _{x \rightarrow 2^{-}} \frac{3}{x-2} \) involves finding the left-hand limit as \( x \) approaches 2. This means we consider values of \( x \) that are slightly less than 2.
02
Substitute Values Approaching from the Left
Since \( x \) approaches 2 from the left (\( x \rightarrow 2^{-} \)), let \( x = 2 - h \) where \( h \) approaches 0 from the positive side. Substitute \( x = 2 - h \) into the expression: \[ \lim_{h \rightarrow 0^{+}} \frac{3}{(2-h)-2} = \lim_{h \rightarrow 0^{+}} \frac{3}{-h} \]
03
Analyze the Behavior of the Fraction
As \( h \) approaches 0 from the positive side, \( -h \) approaches 0 from the negative side (since \( -h \) becomes a small negative number). Therefore, \( \frac{3}{-h} \) approaches negative infinity. This is because dividing 3 by an increasingly small negative number yields an increasingly large negative value.
04
Determine the Limit
Since the fraction \( \frac{3}{-h} \) approaches negative infinity as \( h \rightarrow 0^{+} \), we can conclude that: \[ \lim _{x \rightarrow 2^{-}} \frac{3}{x-2} = -\infty \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Left-hand limit
The concept of the left-hand limit involves analyzing the behavior of a function as the input values approach a specific number from the left side, or the smaller side, of that number. In mathematical notation, this is represented by the addition of a small superscript minus symbol "-" to the number being approached. For example, when we talk about the limit \( \lim_{x \rightarrow 2^{-}} \), we are interested in how the function behaves when \( x \) is getting very close to 2, but stays less than 2. This concept is crucial because functions may behave differently as they approach a number from different sides of the number line.
Understanding left-hand limits helps in determining continuity, whether a function is moving towards a specific finite value, or possibly heading off towards infinity. To evaluate a left-hand limit, choose numbers that are slightly less than the target and observe the resulting function values. This gives insight into the function's behavior as \( x \) approaches the target number from the left.
Understanding left-hand limits helps in determining continuity, whether a function is moving towards a specific finite value, or possibly heading off towards infinity. To evaluate a left-hand limit, choose numbers that are slightly less than the target and observe the resulting function values. This gives insight into the function's behavior as \( x \) approaches the target number from the left.
Approaching behavior
When discussing limits, the 'approaching behavior' of a function describes how the function's output behaves as the inputs draw near to a particular value. It's not just about reaching a number; it's about understanding the trend or pattern as you get closer. For example, if you consider \( \lim_{x \rightarrow 2^{-}} \frac{3}{x-2} \), you're observing how the expression changes as \( x \) gets closer to 2 from the left.
Here's why this is important:
Here's why this is important:
- Understanding if the values are becoming very large, very small, or staying around a certain number.
- This can also indicate the presence of vertical asymptotes, where the function goes to positive or negative infinity.
- In this exercise, as \( x \) increases towards 2 from below, \( x-2 \) gets closer to 0. Therefore, the fraction \( \frac{3}{x-2} \) becomes larger in magnitude, showing the function's tendency to move towards negative infinity.
Infinite limits
Infinite limits occur when the output of a function shoots off towards positive or negative infinity as the input approaches a certain value. This differs from limits that settle on a finite number. In the case of \( \lim _{x \rightarrow 2^{-}} \frac{3}{x-2} \), as described in step 3 of the solution, the behavior of \( \frac{3}{-h} \) as \( h \rightarrow 0^{+} \) shows a trend towards negative infinity.
Here's what to understand about infinite limits:
Here's what to understand about infinite limits:
- An infinite limit suggests a vertical asymptote at the point of interest, where the function doesn’t settle on a finite value but rather increases or decreases without bound.
- For \( \frac{3}{x-2} \), since \( x\) approaches 2 from the left, the function tends to negative infinity, highlighting that it doesn’t converge to a specific number. Instead, it's expressing an infinite declining trend.
- This insight is crucial not only for graphing functions but also for understanding phenomena with no defined bounds, which can apply in real-world scenarios.