Chapter 2: Problem 18
Find the limits. a. \(\lim _{x \rightarrow 1^{+}} \frac{\sqrt{2 x}(x-1)}{|x-1|}\) b. \(\lim _{x \rightarrow 1^{-}} \frac{\sqrt{2 x}(x-1)}{|x-1|}\)
Short Answer
Expert verified
a. \(\sqrt{2}\); b. \(-\sqrt{2}\).
Step by step solution
01
Recognize Type of Limit and Decompose Expression
The given expression is a one-sided limit with a piecewise component due to the absolute value. Recognize that as \(x\) approaches 1 from the right (1+) or left (1-), the absolute value function \(|x-1|\) behaves differently. When \(x \rightarrow 1^{+}\), \(|x-1| = x-1\), and when \(x \rightarrow 1^{-}\), \(|x-1| = -(x-1)\).
02
Limit for Part a: Simplify Expression for x approaching 1 from the Right
For \(x \rightarrow 1^{+}\), \(|x-1| = x-1\). Substitute this into the limit expression: \[\lim_{x \to 1^{+}} \frac{\sqrt{2x}(x-1)}{x-1}.\]Simplify it by cancelling \(x-1\) from the numerator and the denominator: \[\lim_{x \to 1^{+}} \sqrt{2x}.\]Since \(x\) is approaching 1 from the positive side, substitute \(x = 1\):\[\sqrt{2 \times 1} = \sqrt{2}.\]
03
Limit for Part b: Simplify Expression for x approaching 1 from the Left
For \(x \rightarrow 1^{-}\), \(|x-1| = -(x-1)\). Substitute into the limit expression:\[\lim_{x \to 1^{-}} \frac{\sqrt{2x}(x-1)}{-(x-1)}.\]This simplifies to:\[\lim_{x \to 1^{-}} -\sqrt{2x}.\]Since \(x\) approaches 1 from the negative side, substitute \(x = 1\):\[ -\sqrt{2 \times 1} = -\sqrt{2}.\]
04
Compare One-sided Limits
For part (a), the limit as \(x\) approaches 1 from the right is \(\sqrt{2}\), and for part (b), the limit as \(x\) approaches 1 from the left is \(-\sqrt{2}\). Since these limits are not equal, the two-sided limit does not exist at \(x = 1\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
One-sided Limits
One-sided limits are used to examine the behavior of functions as they approach a specific point from one direction only. They help us understand the function's behavior near that point without crossing it. In calculus, these are crucial because they can determine how a function behaves at points where it might not be continuous.
For example, when dealing with the function \(\lim _{x \rightarrow 1^{+}} \, f(x)\), it considers the behavior of \(f(x)\) as \(x\) approaches 1 from the right (positive side). This is distinct from:
If the two-sided limit exists at a point, the one-sided limits from both directions must equal each other at that point.
For example, when dealing with the function \(\lim _{x \rightarrow 1^{+}} \, f(x)\), it considers the behavior of \(f(x)\) as \(x\) approaches 1 from the right (positive side). This is distinct from:
- \(\lim _{x \rightarrow 1^{-}} f(x)\), examining from the left (negative side).
If the two-sided limit exists at a point, the one-sided limits from both directions must equal each other at that point.
Piecewise Functions
Piecewise functions are functions defined by multiple sub-functions, each applied to a specific interval of the domain. These are very useful for modeling scenarios where behavior changes at certain intervals. Consider them like a path with different segments, each with a unique direction.
With piecewise functions, it's crucial to consider:
In this exercise, the absolute value function introduces a piecewise element. The expression involves \(|x-1|\), which behaves differently based on whether \(x\) approaches 1 from above or below. This means two separate rules are applied, leading to different behavior analyzed through one-sided limits.
Fully understanding piecewise functions helps in determining the overall behavior of a compound function, ensuring continuity and evaluating limits correctly.
With piecewise functions, it's crucial to consider:
- The specific formula used within each segment
- The endpoints where segments meet
- Continuity at these endpoints
In this exercise, the absolute value function introduces a piecewise element. The expression involves \(|x-1|\), which behaves differently based on whether \(x\) approaches 1 from above or below. This means two separate rules are applied, leading to different behavior analyzed through one-sided limits.
Fully understanding piecewise functions helps in determining the overall behavior of a compound function, ensuring continuity and evaluating limits correctly.
Absolute Value Analysis
The absolute value function is a critical concept in calculus and is often expressed as \(|x| = x\) if \(x \geq 0\) and \(-x\) if \(x < 0\). It represents the distance of a number from zero on the number line, always yielding non-negative results.
In limit problems, the absolute value becomes essential when handling expressions like \(|x-1|\). Here, the behavior of the absolute value changes:
This piecewise analysis helps distinguish different values or expressions for cases approaching from either side. When examining limits, these variations can cause inequalities between one-sided limits—a vital aspect to note.
Mastering absolute value analysis aids in correctly setting up and simplifying expressions, a fundamental skill to solve calculus problems efficiently.
In limit problems, the absolute value becomes essential when handling expressions like \(|x-1|\). Here, the behavior of the absolute value changes:
- If \(x > 1\), then \(|x-1| = x-1\)
- If \(x < 1\), then \(|x-1| = -(x-1)\)
This piecewise analysis helps distinguish different values or expressions for cases approaching from either side. When examining limits, these variations can cause inequalities between one-sided limits—a vital aspect to note.
Mastering absolute value analysis aids in correctly setting up and simplifying expressions, a fundamental skill to solve calculus problems efficiently.