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Forum URL: http://www.cut-the-knot.org/cgi-bin/dcforum/forumctk.cgi
Forum Name: Middle school
Topic ID: 2
#0, Proof
Posted by Nicole on Oct-18-00 at 04:10 PM

Greetings,

I just had a quick question for you. A few months back, I found a link to a webpage that contained a simple algebraic proof that concluded that All Numbers Were Equal simply by using an a, b and c and simple algebra (no calculus, etc.) There was a flaw in the proof however (one line consisted of subtracting a-b-c but that equaled 0 and thus ruined the rest of the proof but the rest of it made sense...anyway, getting to the point, I tried to go back to that site today and it is no longer available. I was wondering if you knew of such a site (maybe it was just moved to a new location) since you have so many other interesting links on your page. I wanted to show the page to a friend of mine (since we are both math majors) and see if she could spot the flaw.

Thank you for your time.<br>
~N. S.


#1, RE: Proof
Posted by alexb on Oct-18-00 at 04:15 PM
In response to message #0

I am unaware of that site.

You may check


http://www.cut-the-knot.com/do_you_know/mul_eq.html

where there's an example of a similar argument

There's an outstanding book by E.J.Barbeau "Mathematical Fallacies, Flaws, and Flimflam" available at the MAA's bookstore (http://www.maa.org.), where you can find hundreds of much less obvious flawed arguments. Quite indispensable for a math major.

All the best,

Alexander Bogomolny