Chapter 2: Problem 47
Given \(\epsilon>0,\) find an interval \(I=(5,5+\delta), \delta>0,\) such that if \(x\) lies in \(I,\) then \(\sqrt{x-5}<\epsilon .\) What limit is being verified and what is its value?
Short Answer
Expert verified
The limit being verified is \( \lim_{x \to 5^+} \sqrt{x - 5} = 0 \) with \( \delta = \epsilon^2 \).
Step by step solution
01
Understand the Problem
We are given \( \epsilon > 0 \) and need to find an interval \( I = (5, 5+\delta) \) such that for any \( x \) in this interval, \( \sqrt{x-5} < \epsilon \). This means that we are dealing with the expression \( \sqrt{x-5} \) and its behavior as \( x \) approaches 5.
02
Express the Inequality
To solve the problem statement \( \sqrt{x-5} < \epsilon \), we square both sides to remove the square root, leading to the inequality \( x-5 < \epsilon^2 \). This is equivalent to finding \( x \) such that \( 5 < x < 5 + \epsilon^2 \).
03
Define the Interval
From the inequality \( 5 < x < 5 + \epsilon^2 \), we can determine that the interval \( I \) is \( (5, 5+\delta) \) with \( \delta = \epsilon^2 \). Therefore, \( \delta \) must be chosen such that it satisfies this condition.
04
Verify the Limit
The expression we examined is \( \sqrt{x-5} \) as \( x \) approaches 5 from the right. We are essentially verifying the limit \( \lim\_{x \to 5^+} \sqrt{x-5} = 0 \). By finding \( \delta = \epsilon^2 \), we guarantee that the difference \( \sqrt{x-5} \) can be made as small as desired for values just greater than 5.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Limit Verification
Limit verification is an essential part of understanding how a function behaves as it approaches a certain point, in this case, 5. The task involves proving that a particular limit holds true according to its definition. For the problem given, we need to verify the limit:
\[\lim_{x \to 5^+} \sqrt{x-5} = 0\]This means that as x gets closer and closer to 5 from the right, the value of \( \sqrt{x-5} \) should approach 0. Limit verification ensures that for every small number (epsilon) we choose, there is a corresponding small interval (delta) from which any x will make \( \sqrt{x-5} \) smaller than epsilon.
Here's more to understand about how this works:
\[\lim_{x \to 5^+} \sqrt{x-5} = 0\]This means that as x gets closer and closer to 5 from the right, the value of \( \sqrt{x-5} \) should approach 0. Limit verification ensures that for every small number (epsilon) we choose, there is a corresponding small interval (delta) from which any x will make \( \sqrt{x-5} \) smaller than epsilon.
Here's more to understand about how this works:
- You have an epsilon \((\epsilon > 0)\), which is any small positive number that we choose.
- Delta \((\delta)\) must be found such that for every x in the interval \((5, 5+\delta)\),
\( \sqrt{x-5} < \epsilon \). - The goal is to find how small \( \delta \) needs to be to make the inequality hold true, thus verifying the limit.
Epsilon-Delta Definition
The epsilon-delta definition is a formal way to define what it means for a function to have a limit. This is a crucial concept in calculus that tells us exactly when a function approaches a limit at a certain point. It's designed to be rigorous to eliminate ambiguity.
In simple terms, the epsilon-delta definition states:
In simple terms, the epsilon-delta definition states:
- For every \( \epsilon > 0 \), there exists a \( \delta > 0 \) such that if \( 0 < x - 5 < \delta \),
then \( |\sqrt{x-5} - 0| < \epsilon \).
- If we want \( \sqrt{x-5} \) to be less than \( \epsilon \), we must frame \( x \) nearer to 5 such that \( x \) lies in the vicinity of 5, specifically just a delta distance to the right of 5.
- This interval makes sure the function values stay within the small boundary \( \epsilon \), confirming the limit.
Right-Hand Limits
Right-hand limits are a specific type of limit where we observe the behavior of a function as the variable approaches a certain number from the right. In our exercise, this implies examining how \( \sqrt{x-5} \) behaves as \( x \) comes closer to 5 from values greater than 5.
This is noted mathematically as \( \lim_{x \to 5^+} \sqrt{x-5} \), indicating the limit is evaluated as x approaches from the right side. Here's what you need to understand about right-hand limits:
Therefore, in proofs or verifications, focusing on one side helps in conclusive arguments about a function's limit as it helps map out exact scenarios that the epsilon-delta definition capitalizes on.
This is noted mathematically as \( \lim_{x \to 5^+} \sqrt{x-5} \), indicating the limit is evaluated as x approaches from the right side. Here's what you need to understand about right-hand limits:
- The approach is one-sided – we only consider values of x that are just over the number in question (here, 5).
- This is different from a two-sided limit where both left and right approaches are considered.
- When working with right-hand limits, you use delta to describe distances where \( x \) is always just a step greater than 5.
Therefore, in proofs or verifications, focusing on one side helps in conclusive arguments about a function's limit as it helps map out exact scenarios that the epsilon-delta definition capitalizes on.