How Does the (ε, δ)-Definition of Limit Apply to lim x->a x^5=a^5?

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Discussion Overview

The discussion revolves around the application of the (ε, δ)-definition of limit to the expression lim x->a x^5=a^5. Participants explore the challenges of using symbolic constants in the context of limits and seek clarification on how to approach the problem without specific numerical values.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant expresses confusion about using symbolic constants instead of specific numbers when applying the (ε, δ)-definition of limit.
  • Another participant questions whether the problem would be easier to solve if a specific number, such as a = 2, were used instead of a symbolic constant.
  • A participant reiterates the original question, emphasizing the lack of a specific number as a source of difficulty in solving the problem.
  • One participant proposes a method involving δ=ε/M, where M is defined as max|x^4+ax^3+...+a^4|, to establish the relationship between |x^5-a^5| and |x-a|.
  • There is a suggestion that understanding the general idea behind the limit is crucial, regardless of whether a is a symbolic constant or a specific number.

Areas of Agreement / Disagreement

Participants generally agree on the challenges posed by the use of symbolic constants in the limit definition, but there is no consensus on how to best approach the problem or whether using a specific number would simplify the exercise.

Contextual Notes

Participants note that the lack of a specific numerical value may complicate the application of the (ε, δ)-definition, and there are unresolved questions about the generalizability of the approach to different values of a.

wonnabewith
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I have a question about the (ε, δ)-definition of limit
lim x->a x^5=a^5
I know that |x^5-a^5|<ε
and |x-a|<δ
I was confused when using letters instead of actual number to solve this problem
the goal of this problem is to show that lim x->a x^5=a^5 is true

I will be glad to get some help...
thanks
 
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If there was not a symbolic constant like a, but a number such as a = 2, would you be able to solve the exercise?
 
the original question is :"use the ε, δ-definition of limit to show that lim x->a x^5=a^5
there is no actual number in it, that's why I'm stuck when I was solving the problem
 
For all ε>0, there exists δ=ε/M (M=max|x^4+ax^3+...+a^4|) such that
|x^5-a^5|=|x-a||x^4+ax^3+...+a^4|<δM=ε whenever |x-a|<δ
 
CompuChip said:
If there was not a symbolic constant like a, but a number such as a = 2, would you be able to solve the exercise?

wonnabewith said:
the original question is :"use the ε, δ-definition of limit to show that lim x->a x^5=a^5
there is no actual number in it, that's why I'm stuck when I was solving the problem
If you post a problem and one of the most helpful members of this forum asks a question about it, it is a good idea to answer that question!

You said earlier "I was confused when using letters instead of actual number" so compuchip wanted to see how you would do it if it had been "2" instead of "a". Then he could guide you to the "general" idea.

Where it is "a" or "2", the basic idea needed here is that x^5- a^5= (x- a)(x^4+ ax^3+ a^2x^2+ a^3x+ a^4)
 

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