Is a < b+ε for all ε>0 true if a is not ≤ b?

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Homework Help Overview

The discussion revolves around the relationship between two numbers, "a" and "b", specifically examining the assertion that if "a" is less than "b + ε" for all ε > 0, then "a" must be less than or equal to "b". Participants are exploring the implications of this statement in the context of real numbers.

Discussion Character

  • Conceptual clarification, Assumption checking, Exploratory

Approaches and Questions Raised

  • Some participants attempt to use specific numerical examples to illustrate the relationship between "a" and "b", questioning whether this approach is valid for a general proof. Others suggest considering the implications of assuming "a" is not less than or equal to "b" and how that might contradict the original statement.

Discussion Status

The discussion is active, with participants offering different perspectives on the validity of using specific numbers versus general reasoning. There is an exploration of the implications of the original statement, and some guidance is provided regarding the nature of the proof being sought.

Contextual Notes

Participants note that the problem pertains to real numbers rather than integers, emphasizing the need for a general proof rather than reliance on specific cases.

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Homework Statement



Supopse that "a" and "b" are two numbers and that a < b+ε for all ε>0. Show that a ≤ b

Homework Equations



None given for problem

The Attempt at a Solution



See attachment of my jpeg for my attempt. I'm not sure, but i feel like it satisfies the statement
 

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The graph does not constitute an argument. I would not even consider drawing a graph for this question (unless instructed to). Or are you just checking you have understood the question?
 
haruspex said:
The graph does not constitute an argument. I would not even consider drawing a graph for this question (unless instructed to). Or are you just checking you have understood the question?

For problems like these, can I use real numbers to try and figure it out?

Assuming a = 5 and b + e = 6. These two values would work because 5 < 6. Since e > 0, it has to be a positive number. To make things easy, we'll pick the smallest positive integer greater than zero: 1. If e becomes equal to 1, then I can say that b is equal to 5. Now I can say that a = b, which satisfies the first part of the second equation.

"b" can be greater than "a" if I pick any number I want "b" to equal, so long as it is greater than "a" by a substantial amount.

Algebraically, I could write that

a < b when e > (b-a), and a = b when e = (b-a) ?
 
This is not a question about integers, I'm sure. It's about reals. And no argument based on specific numbers could be considered a general proof.
Try reductio ad absurdum: assume a is not <= b and see if you can demonstrate this violates "a < b+ε for all ε>0".
 

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