Proving Negative Real Numbers Using Contradiction

In summary, the conversation discusses the topic of proving by contradiction that a real number which is less than every positive real number cannot be positive. The conversation includes a request for help and a hint given, but the person is still unable to proceed. It is also mentioned that the person should show some effort before receiving help.
  • #1
zoxee
37
0
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?
 
Physics news on Phys.org
  • #2
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]?
 
  • #3
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 :(
 
  • #4
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?
 
  • #5
I wouldn't even bother with x/2. Suppose x is positive. Can it then be "less than every positive number"
 
  • #6
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.
 

What is "Proving Negative Real Numbers Using Contradiction"?

"Proving Negative Real Numbers Using Contradiction" is a mathematical method used to prove that a number is negative by assuming the opposite (that it is positive) and showing that it leads to a contradiction.

Why is "Proving Negative Real Numbers Using Contradiction" important?

"Proving Negative Real Numbers Using Contradiction" is important because it allows us to prove the existence of negative real numbers, which are crucial in many mathematical concepts and real-life applications. It also helps to strengthen our understanding of mathematical proofs and logic.

How does "Proving Negative Real Numbers Using Contradiction" work?

"Proving Negative Real Numbers Using Contradiction" works by assuming that the number in question is positive and then using mathematical operations and logical arguments to arrive at a contradiction, thus proving that the number must be negative. This method is based on the principle of proof by contradiction.

What is the difference between "Proving Negative Real Numbers Using Contradiction" and "Proving Positive Real Numbers Using Contradiction"?

The main difference between these two methods is the starting assumption. In "Proving Negative Real Numbers Using Contradiction", we assume that the number is positive and try to reach a contradiction, while in "Proving Positive Real Numbers Using Contradiction", we assume that the number is negative and try to reach a contradiction.

Are there any limitations to "Proving Negative Real Numbers Using Contradiction"?

Yes, there are limitations to this method. It may not work in every scenario and may require additional assumptions or conditions to be proven. It also relies on the concept of proof by contradiction, which may not be applicable in all mathematical proofs. Furthermore, it may not be the most efficient method in some cases and may require a lot of steps and calculations.

Similar threads

  • Precalculus Mathematics Homework Help
Replies
18
Views
1K
  • Precalculus Mathematics Homework Help
Replies
10
Views
2K
  • Precalculus Mathematics Homework Help
Replies
12
Views
3K
  • Calculus and Beyond Homework Help
Replies
3
Views
128
  • Math Proof Training and Practice
Replies
4
Views
1K
  • Precalculus Mathematics Homework Help
Replies
4
Views
1K
  • Precalculus Mathematics Homework Help
Replies
5
Views
2K
  • Precalculus Mathematics Homework Help
Replies
18
Views
2K
Replies
7
Views
2K
  • Calculus and Beyond Homework Help
Replies
13
Views
714
Back
Top