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Algebraic paradox

Amusement for the grey matter

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Brian Wood05/01/2019 10:04:04
2742 forum posts
39 photos

I found this in an old book of collected Mathematical puzzles selected from Scientific American magazine. It is the leader in my album pictures, I'm not sure how to include it in the text here

The logic appears to be impeccable and it will work if 'c' is assigned the value of zero, but the general expression is compelling. I can imagine it it will appeal to Michael G especially

Enjoy

Brian

Edited By Brian Wood on 05/01/2019 10:05:41

Edited By Brian Wood on 05/01/2019 10:06:31

John Hinkley05/01/2019 10:08:07
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1545 forum posts
484 photos

Very puzzling! What exactly is the puzzle? Or is that what we're should be trying to figure out? Should even be a challenge for Michael G.

John

Michael Gilligan05/01/2019 10:09:54
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23121 forum posts
1360 photos

**LINK**

https://www.model-engineer.co.uk/albums/member_photo.asp?a=49837&p=820787

... I must leave it 'til later

MichaelG.

JasonB05/01/2019 10:10:07
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25215 forum posts
3105 photos
1 articles

Easy enough to work out what the puzzel is even without Michaels helpwink 2

Edit, beat me to it.

Edited By JasonB on 05/01/2019 10:11:20

Andrew Johnston05/01/2019 10:15:35
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7061 forum posts
719 photos

If c is zero then a-b is also zero so in the first step you multiply both sides by zero - to get 0=0. Just goes to show Kurt Godel was right.

Andrew

John Hinkley05/01/2019 10:16:12
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1545 forum posts
484 photos

Didn't think to look there!

John

Gary Wooding05/01/2019 10:45:10
1074 forum posts
290 photos

The real answer is that if A=B+C then A-B-C=0, so,

after factorisation you have Ax0 = Bx0, which is clearly correct for all values of A and B

John Haine05/01/2019 10:58:58
5563 forum posts
322 photos

And it isn't a paradox.

Andrew Tinsley05/01/2019 11:05:41
1817 forum posts
2 photos

The real snag is that you divide both sides by a-b-c which is equal to zero. Dividing by zero is a no, no as the result can have any value.

Andrew.

pgk pgk05/01/2019 11:29:18
2661 forum posts
294 photos

As is pointed out a-b-c=0 so as soon as you move ac to the left side of the equation you have 0=0

Georgineer05/01/2019 16:25:52
652 forum posts
33 photos

In my school days we had a proof that any number was greater than any number greater than itself, also achieved by the same trick of a hidden division by zero. There was also a geometrical proof that all right angles are obtuse. Regrettably, the details have evaporated in the ensuing half-century.

George

not done it yet05/01/2019 18:14:56
7517 forum posts
20 photos
Posted by Andrew Tinsley on 05/01/2019 11:05:41:

The real snag is that you divide both sides by a-b-c which is equal to zero. Dividing by zero is a no, no as the result can have any value.

Andrew.

Only zero divided by zero is indeterminate. Zero divided into anything else is actually infinity. The indeterminacy arises because the answer of any number divided by itself is one.

Tim Stevens05/01/2019 23:00:04
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1779 forum posts
1 photos

And as every schoolboy knows, (to end with a political message) there is nothing more indeterminate than unity.

Cheers, Tim

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