Proving Negative Real Numbers Using Contradiction

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Homework Help Overview

The discussion revolves around proving by contradiction that a real number which is less than every positive real number cannot itself be positive. Participants are exploring the implications of this statement within the context of real numbers.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to understand the implications of assuming a positive real number exists that is less than every positive real number. Questions arise about the nature of such a number, particularly regarding the value of x/2 and its positivity.

Discussion Status

There is ongoing exploration of the assumptions involved in the problem. Some participants are questioning the validity of a positive number being less than all positive numbers, while others are seeking hints to advance their reasoning.

Contextual Notes

Participants are reminded of forum rules that require them to demonstrate effort before receiving further assistance, indicating a focus on the learning process.

zoxee
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Prove by contradiction that a real number that is less than every positive real number cannot be positive

having troubles with this

could someone give me a small hint to get started?
 
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zoxee said:
Prove by contradiction that a real number that is less than every positive real number cannot be positive

having troubles with this

could someone give me a small hint to get started?

Suppose [itex]x > 0[/itex] is such that every positive real number is greater than or equal to [itex]x[/itex]. What then is [itex]x/2[/itex]?
 
pasmith said:
Suppose [itex]x > 0[/itex] is such that every positive real number is greater than or equal to [itex]x[/itex]. What then is [itex]x/2[/itex]?

I'm sorry but I can't seem to proceed even with this hint :(
 
zoxee said:
I'm sorry but I can't seem to proceed even with this hint :(

Given that [itex]x[/itex] is a positive real number, is [itex]x/2[/itex] a positive real number?
 
I wouldn't even bother with x/2. Suppose x is positive. Can it then be "less than every positive number"
 
zoxee said:
Prove by contradiction that a real number that is less than every positive real number cannot be positive

having troubles with this

could someone give me a small hint to get started?

Please check your PMs. The PF Rules require that you show some effort before we offer tutorial help.
 

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