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#2 2009-04-26 04:22:30
- JaneFairfax
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Re: 1=2 proof
Why do you want to learn incorrect proofs? Much better if you just concentrate on learning correct proofs. That might help you pass your exams.
#4 2009-04-26 17:17:53
- bobbym
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Re: 1=2 proof
Hi dreamalot;
I'm afraid Jane is right about learning correct proofs but if you are determined to see this, here is a link that I know of.
http://en.wikipedia.org/wiki/False_proof
Last edited by bobbym (2009-05-15 15:32:18)
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#5 2009-06-12 20:48:52
- DarkLightA
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Re: 1=2 proof
That's the first false proof I've found the fault in 
Division by 0.. (a-b), where a=b
#6 2009-06-13 21:03:28
- JaneFairfax
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Re: 1=2 proof
Here is another “proof” that 1 = 2, one that doesn’t make use of division by 0.
Last edited by JaneFairfax (2009-06-13 21:05:48)
#7 2009-06-14 02:05:24
- bobbym
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Re: 1=2 proof
Hi Jane;
I know you are not posing this as a problem but
Line 1 identity
Line 2 identity
As near as I can figure the problem is with the third statement, the taking of the square root of both sides.
which is only true for
Last edited by bobbym (2009-06-14 16:17:15)
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#11 2009-08-04 17:32:58
- bobbym
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Re: 1=2 proof
Hi amhore;
Jane wrote:
Why do you want to learn incorrect proofs? Much better if you just concentrate on learning correct proofs. That might help you pass your exams.
She is still right.
About half way down the page.
click me for false proofs
Last edited by bobbym (2009-08-05 03:32:39)
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#13 2009-08-05 03:35:15
- bobbym
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Re: 1=2 proof
Welcome manzil
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#16 2010-07-20 05:31:04
- bobbym
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Re: 1=2 proof
Hi santhosh;
JaneFairfax wrote:
Jane wrote:
Why do you want to learn incorrect proofs? Much better if you just concentrate on learning correct proofs. That might help you pass your exams.
She is still right.
She is even more correct!
Welcome to the forum!
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#17 2010-08-07 06:19:29
- jk22
- Member
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Re: 1=2 proof
Hi,
we have not 1=2, except if units are e.g. $ and £ in the year (to find, e.g. in the y 1976, or 1978 http://www.miketodd.net/encyc/dollhist.htm)...1£=2$ were at some time of the story of humanity.
but we were allowed to write
2 is equivalent to 0 (modulo 2)
divide by 2 and
1 is equivalent to 0 (modulo 1).
Last edited by jk22 (2010-08-07 06:51:45)
#18 2010-08-07 07:03:55
- bob bundy
- Moderator
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Re: 1=2 proof
Actually, I don't think there's any harm studying 'false' proofs as long as you're aware that there is something wrong with the proof.
That way you learn something about what is allowable in a proof and what isn't.
In the example that started this thread, for example, you should learn that dividing by zero is not acceptable in algebra.
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#20 2011-05-07 04:07:33
- sur_arijit01
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Re: 1=2 proof
plz help me 2 find out the wrong step:all digits are equal just putting values of x,y
s1) -x.y=-x.y
s2) x^2-x(x+y)=y^2-y(x+y)
s3) x^2-2x(x+y)/2+{(x+y)/2}^2 = y^2-2y(x+y)/2+{(x+y)/2}^2
s4) {x-(x+y)/2}^2 = {y-(x+y)/2}^2
s5) x-(x+y)/2 = y-(x+y)/2
s6) x=y
#21 2011-05-07 04:39:21
- bob bundy
- Moderator
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Re: 1=2 proof
hi sur_arijit01
It looks to me like S4 -> S5 is the faulty step.
Just because a^2 = b^2 you may not conclude that a = b eg. 9 = 9 but + 3 is not equal to -3
But if you write
s5) x-(x+y)/2 = -(y-(x+y)/2)
then you get x + y = x + y which seems more reasonable.
Bob
footnote: When I'm trying to track down an algebraic error the following sometimes works.
Choose a value for x and another for y. (Best to avoid 0 and 1 here)
If the value of the LHS = RHS then there's a strong chance the steps to that point are OK.
When LHS not = RHS you know a false step has occurred.
Last edited by bob bundy (2011-05-07 04:45:09)
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#22 2011-06-20 01:54:29
- joker30
- Guest
Re: 1=2 proof
You can proof substitution with number, no need to let x=y.
10² = 100 (right)
10²-10²=100-100
(10-10)(10+10)=10(10-10)
So,
(10+10)=10
20=10
2=1
#23 2011-06-20 02:35:39
- bobbym
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Re: 1=2 proof
Hi joker30;
Welcome to the forum!
That is a little bit of a twist!
In mathematics, you don't understand things. You just get used to them.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.
#24 2011-06-20 02:58:43
- bob bundy
- Moderator
Online
Re: 1=2 proof
hi joker30
OK, but it's still a case of:
in post #18, I wrote:
In the example that started this thread, for example, you should learn that dividing by zero is not acceptable in algebra.
except substitute 'number calculations' for 'algebra'.
Bob
Last edited by bob bundy (2011-06-20 03:00:55)
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#25 2011-06-20 04:15:59
- reconsideryouranswer
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Re: 1=2 proof
ganesh wrote:
Here is another:-
But this proves 2 > 3.
3 < 2
You're missing required grouping symbols, ganesh.
One of the lines above can be fixed by typing:
Signature line:
I wish a had a more interesting signature line.