Can anyone spot the error in this fallacy

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Discussion Overview

The discussion revolves around a mathematical fallacy involving the manipulation of equations to conclude that all numbers are the same. Participants analyze the steps taken in the proof, particularly focusing on the implications of taking square roots and the conditions under which the equations hold true.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants point out that the error occurs when taking the square root in the transition from the sixth to the seventh line, emphasizing the need to consider both positive and negative roots.
  • Others argue that the mathematical steps seem valid but lead to inconsistencies when specific values are substituted, suggesting that the proof does not hold for all cases.
  • A participant asserts that the proof incorrectly concludes that a and b must be equal, highlighting that the equations only imply a = b under certain conditions.
  • Some participants express confusion over the calculations, questioning the validity of the results obtained from the fifth and sixth lines when specific numbers are used.
  • A later reply proposes a corrected version of the proof, indicating that a can equal b or a can equal t - b, thus allowing for the possibility that the numbers are not necessarily the same.
  • Another participant mentions that the original proof resembles other logical fallacies that incorrectly assert equivalences, such as 1 = 2.

Areas of Agreement / Disagreement

Participants generally disagree on the validity of the proof and the implications of the mathematical manipulations. There is no consensus on whether the original argument is sound, as multiple viewpoints and interpretations of the steps are presented.

Contextual Notes

Limitations include the potential misunderstanding of square root properties and the assumptions made about the values of a, b, and t. The discussion highlights the importance of careful mathematical reasoning and the conditions under which certain equations hold.

Who May Find This Useful

This discussion may be of interest to those studying mathematics, particularly in understanding common fallacies and the importance of rigor in mathematical proofs.

  • #31
Sorry! said:
I think what you mean to say is all numbers within the sets are the same. Not all numbers are the same.
The set of numbers is a set.
 
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  • #32
jimmysnyder said:
The set of numbers is a set.

Yes but saying that set A has the same numbers as set B is far different from saying the numbers contained within the sets are the same. 1 is not the same as 2, however the set A {1,2} is the numbers as set B {2,1}
 
  • #33
Sorry! said:
Yes but saying that set A has the same numbers as set B is far different from saying the numbers contained within the sets are the same. 1 is not the same as 2, however the set A {1,2} is the numbers as set B {2,1}
I did not say that A has the same numbers as B. For instance, in the example I gave, A had 4 elements and B had 3. What I did say is that if you assume ... Hey wait a minute. You do know what mathematical induction is right? I am doing induction on the number of elements in the set. Do you understand what that means? Can you do an inductive proof that the sum of the first n positive integers is equal to n(n + 1) /2?
 
  • #34
Sorry! said:
We are not taking the square root of any negative numbers here.

In order to go from:

(a - t/2)^2 = (b - t/2)^2

To:

a - t/2 = b - t/2

Where a, b, and t are variables for all real numbers, then yes, you are...

Well, you're excluding have the input set, the half where either a-t/2 is negative, or b-t/2 is negative.
 
  • #35
jimmysnyder said:
I did not say that A has the same numbers as B. For instance, in the example I gave, A had 4 elements and B had 3. What I did say is that if you assume ... Hey wait a minute. You do know what mathematical induction is right? I am doing induction on the number of elements in the set. Do you understand what that means? Can you do an inductive proof that the sum of the first n positive integers is equal to n(n + 1) /2?

I thought what you were doing was using a,b,c,d to represent specific numbers. and in each set they would represent the same numbers. I do know what mathematical induction is though.
 
  • #36
mugaliens said:
In order to go from:

(a - t/2)^2 = (b - t/2)^2

To:

a - t/2 = b - t/2

Where a, b, and t are variables for all real numbers, then yes, you are...

Well, you're excluding have the input set, the half where either a-t/2 is negative, or b-t/2 is negative.

So I guess when I take I take:
\sqrt(1-2)^2 or
\sqrt(-3)^2
(the line should be over everything but I'm not great with latex.
I'm taking the square root of a negative number... interesting; never learned that in math.

Let's see what happens when we follow order of operations:
\sqrt(-3)^2=<br /> \sqrt(9)=+/-3

Where do we take the square root of any negative number?
 
  • #37
Where in the OP did it say real number? If a is i (imaginary) and t is 0, then a - t/2 is i and its square is -1. When you take the square root you will be taking the square root of a negative number. But that is not the flaw in the proof.
 
  • #38
jimmysnyder said:
Where in the OP did it say real number? If a is i (imaginary) and t is 0, then a - t/2 is i and its square is -1. When you take the square root you will be taking the square root of a negative number. But that is not the flaw in the proof.

lol, i think i hate you.

:-p

jkz :)
 
  • #39
Sorry! said:
jkz
ndrstd
 
  • #40
By the way, if you quote this post, it will show you how to extend the line of the square root symbol

\sqrt{(-3)^2}=<br /> \sqrt{(9)}=\pm3
 
  • #41
jimmysnyder said:
By the way, if you quote this post, it will show you how to extend the line of the square root symbol

\sqrt{(-3)^2}=<br /> \sqrt{(9)}=\pm3

OHHHH ok thanks. I tried using those [] brackets but it was just leaving a huge space. Thanks jimmy :smile:
 
  • #42
I am locking this thread. The OP has not been back since his initial post.
 

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