A -ve number greater than infinity?

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Discussion Overview

The discussion revolves around the concept of dividing a positive number by increasingly smaller values, including negative values, and the implications of such operations on the notion of infinity. Participants explore the behavior of the function 5/x, its graphical representation, and the mathematical reasoning behind limits and asymptotic behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant argues that as the denominator in 5/x decreases, the output increases, leading to the conclusion that -5 must be greater than infinity.
  • Another participant points out that the curve 5/x is a rectangular hyperbola and is asymptotic, implying it approaches infinity but never reaches it.
  • Some participants challenge the assumption that a function that is increasing for some values must always be increasing.
  • There is a discussion about the limit of 5/x as x approaches 0, with some clarifying that it approaches positive or negative infinity depending on the direction of approach.
  • One participant presents a separate argument using squares, suggesting that just because a property holds for a certain range does not mean it applies outside that range.
  • Another participant emphasizes that the graph of 5/x decreases from negative to positive infinity, contradicting the initial claim of it increasing.
  • Participants also discuss the nature of hyperbolas in relation to the function 5/x, noting that it does not represent a straight line.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the behavior of the function 5/x, the concept of infinity, and the validity of the arguments presented. The discussion remains unresolved with no consensus on the interpretations of the mathematical claims.

Contextual Notes

Limitations include the dependence on definitions of infinity, the behavior of functions near discontinuities, and the assumptions made about the continuity of functions across different ranges.

AlbertEinstein
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Please follow the following arguments.
5/3=1.66
5/2=2.5
5/1=5
5/0.5=10
...
...
5/0=infinity
and then 5/(-1)= -5
What you see? As the denominator is decreased the right hand side answer increases. The denominator becomes 3 then 2,then 1, then 0,then -1 ; and the answer increases, therefore -5 must be grater than infinity.
Where's the flaw. Please illustrate.
 
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AlbertEinstein said:
and the answer increases, therefore -5 must be grater than infinity.
Where's the flaw. Please illustrate.

In assuming that because for some set of values f(x) is increasing it is always increasing.
 
Mainly, your answer doesn't work because 5 is a prime number.
 
As one divides by smaller and smaller numbers, the output figure approaches but does not reach infinity, no?
 
Depends on your notion of smallness.
 
Please follow the following arguments.

5=5
4=4
3=3
2=2
1=1
0=0
-1=-1

What do you see? As the left hand side decreases, the right hand side is greater than or equal to zero. Therefore, -1 must be greater than or equal to zero.

Ja?

Just because a property holds true for a certain range of numbers, it doesn't mean the pattern will follow for numbers outside that range. That's the flaw.
 
AKG said:
Mainly, your answer doesn't work because 5 is a prime number.
:smile: :smile: That's funny.
 
Gokul43201 said:
:smile: :smile: That's funny.

It is? :confused:
 
  • #10
Ya, its funny because AKG's answer isn't right.
ja ja
 
  • #11
5/0 does not equal infinity. The limit of 5/x as x approaches 0 equals inifinty.
 
  • #12
daveb said:
5/0 does not equal infinity. The limit of 5/x as x approaches 0 equals inifinty.
In absolute value, yes. But else you have to mind the sign, depending on whether you're approaching 0 from the left or right, you get -inf resp. +inf.
 
  • #13
I don't see how you can say that -1 is greater than or equal to 0. I might be horribly wrong but what I think you're doing is just equating numbers & two equal numbers are always equal .. under no circumstances can be greater than or equal to.

Look at this order:

1=1
9=9
8=8
-1=-1

Don't you see?
 
  • #14
Albert:

Please follow the following arguments.
(x^2=y)
3^2=9
2^2=4
1^2=1
0^2=0
-1^2=1

What you see? As the x value is decreased, the y value (right hand side answer) decreases. The x value becomes 3 then 2,then 1, then 0,then -1 ; and the answer (y) decreases, therefore 1 must be less than zero.

Now where's the flaw?


(Hint: the only flaw is the conclusion that a given function must result in a straight and continuous line.)
 
Last edited:
  • #15
Okay...let me try to hit this topic.
Graphing 5/x you will have a line that going from negative infinity to positive infinity it ALWAYS DECREASES. it never increases. However, it starts out negative and ends up positive.

Lesson learned today: Don't mess with the division by zero.
 
  • #16
Robokapp said:
Okay...let me try to hit this topic.
Graphing 5/x you will have a line that going from negative infinity to positive infinity it ALWAYS DECREASES. it never increases. However, it starts out negative and ends up positive.

Lesson learned today: Don't mess with the division by zero.

No you do not have a line. You have a hyperbola in the first and third quandrants of the cartesian plane.
 
  • #17
Here am a graph of 1/x.
http://www.mathsrevision.net/gcse/1overx.gif
5/x follows the same pattern.
 
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