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8 replies to this topic

#1 Panda_ca

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Posted 15 January 2008 - 07:04 AM

The following is what seems to be a mathematical proof that two equals one. What's wrong with it?

a = b
aa = ab
aa - bb = ab - bb
(a + b)(a - b) = b(a - b)
a + b = b
a + a = a
2a = a
2 = 1
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#2 bonanova

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Posted 15 January 2008 - 07:09 AM

Spoiler for Dividing by

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The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
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#3 Maximus

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Posted 25 January 2008 - 08:40 PM

how do you go from.........a + b = b
to........a + a = a
the top line just means a=0?
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#4 x-Genius-Girl-007-x

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Posted 26 January 2008 - 09:34 PM

a must equal zero right?
aargh confusing much ??
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#5 Jkyle1980

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Posted 26 January 2008 - 10:46 PM

how do you go from.........a + b = b
to........a + a = a
the top line just means a=0?


Because a = b, he can substitute a and b freely for each other.
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#6 Aunt Minta

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Posted 29 January 2008 - 09:03 PM

The following is what seems to be a mathematical proof that two equals one. What's wrong with it?

a = b
aa = ab
aa - bb = ab - bb
(a + b)(a - b) = b(a - b)
a + b = b
a + a = a
2a = a
2 = 1


The problem is with the division in the fourth line. You have to divide each element on the left side of the equation by (a-b). The fifth line should be (a+b)/(a-b)=b
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#7 brhan

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Posted 30 January 2008 - 02:33 PM

The problem is with the division in the fourth line. You have to divide each element on the left side of the equation by (a-b). The fifth line should be (a+b)/(a-b)=b


You got it wrong, brother. The division was ok in a sense, you divide both the left and right sides by the same number other than zero. The problem here is dividing both sides -- the left and right sides -- by zero. From basic maths we know that when a number is divided by zero, it would be undefined.
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#8 bonanova

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Posted 30 January 2008 - 04:00 PM

You got it wrong, brother. The division was ok in a sense, you divide both the left and right sides by the same number other than zero. The problem here is dividing both sides -- the left and right sides -- by zero. From basic maths we know that when a number is divided by zero, it would be undefined.

I'll bet Aunt Minta is probably a sista. B))
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The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
- Bertrand Russell

#9 brhan

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Posted 30 January 2008 - 05:24 PM

I'll bet Aunt Minta is probably a sista. B))


Thanx Bonanova, I agree. I just didn't notice the name. :P

What do you think the odds would be that Auntie is a man?

Edited by brhan, 30 January 2008 - 05:27 PM.

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