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1 = 2 
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Post 1 = 2
assume that... a = b
(a ^ 2) = ab
(a ^ 2) - ab = 0
2((a ^ 2) - ab) = 0
(a ^ 2) - ab = 2((a^2) - ab)
a(a - b) = 2a(a - b)
(a(a - b)) / (a(a - b)) = (2a(a - b)) / (a(a - b))
1 = 2

I kinda freaked out when I saw this today, until I realized why it happens... if a=b, then a-b=0... so the fact that you're dividing both sides by a(a - b) means that you are dividing by zero, thus the parts in bold are invalid (since (n / 0) is an illegal operation).

Anyone else got any more of these kind of equations?


Mon Jan 12, 2009 6:53 pm
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that statement is a bunch of logic fail long before you get to division. Its the reverse application of Occam's razor. You are supposed to reduce complexity, not increase it.

a = b
ok lets get b on the same side as a, so lets subtract b from both sides.
a - b = 0
at this point we are done, there is nothing more we need to do here. a = b as long as they are the same value.

even if you had a valid reason to multiply both sides by a, the approach is off

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Last edited by funkyass on Mon Jan 12, 2009 8:05 pm, edited 1 time in total.



Mon Jan 12, 2009 7:52 pm
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No, assuming that a = b (which of course means that they are both of the same value), everything except the bold-highlighted and underlined parts are valid. It's just once of those neat little tricks: you give them this equation and they are shocked that 1 somehow = 2, until they realize the the division by zero.

I could easily use this to make it look as if 1 = 9999 as well:
(a ^ 2) = ab
(a ^ 2) - ab = 0
9999((a ^ 2) - ab) = 0
(a ^ 2) - ab = 9999((a^2) - ab)
a(a - b) = 9999a(a - b)
(a(a - b)) / (a(a - b)) = (9999a(a - b)) / (a(a - b))
1 = 9999

But of course we know this isn't true; as has been mentioned, it's a mathematical practical-joke.

Yeah sure occam's razor. Keep things as simple as possible and all that, and use the least amount of assumptions possible, but that wasn't the point here.

Quote:
even if you had a valid reason to multiply both sides by a, the approach is off

It was a necessary step to get to the part where you make it look like 1 = 2.


Mon Jan 12, 2009 8:00 pm
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you must have sucked at algebra.

there is no reason to multiple both sides by a on the second line, nor is multiplication by 2 on the fourth line. Its not a practical joke, its a meme transmitted by those who never really paid much attention in junior high math.

heck, your proof is proving that.

a=b
a^2 = ab lets multiply by a for no good reason;
2a^2 = 2ab multiply by 2;
2a^2 - 2ab = 0 get all terms on one side;
2a(a-b) = 0 collect like terms;
a-b = (0/2a) divide by 2a
a = (0/2a) +b add b;
a = b since zero divided by anything is zero, we can toss (0/2a);

incompetence never leads to a practical joke.

a practical joke is disassembling a teachers car, and reassembling it in their office as a a fully electric vehicle. Shooting your own foot isn't a practical joke.

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Mon Jan 12, 2009 8:15 pm
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...I suck at algebra. Heh.
Yeah, ok mum.

Hey, news flash: at no time during my creating this thread did I intend to be serious. :roll:
Psst psst: I didn't even create this; I got it from http://forums.xkcd.com/viewtopic.php?f=17&t=8119


Mon Jan 12, 2009 8:29 pm
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it's a classic "proof" to mess with the minds of people who enjoy math.

Every operation performed is perfectly valid - it's just the result of the division by zero that's incorrect.


Mon Jan 12, 2009 9:14 pm
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there is no division by zero... zero is divided by a number, but nothing is divided by zero anywhere in any proofs in this thread.

it a classic incorrect proof... but for fucks sake understand why its incorrect...

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Mon Jan 12, 2009 9:22 pm
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funkyass wrote:
there is no division by zero... zero is divided by a number, but nothing is divided by zero anywhere in any proofs in this thread.

it a classic incorrect proof... but for fucks sake understand why its incorrect...

Yes there is.

IT'S THE LAST STEP.
He divides left and right by a value that's equal to 0/0.
Hello. Sorry. Have a nice day.

For instance I much prefer the one where it's much more subtly done. I shall go dig for it in case i still have it somewhere.

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Mon Jan 12, 2009 9:54 pm
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Quote:
there is no division by zero... zero is divided by a number, but nothing is divided by zero anywhere in any proofs in this thread.

it a classic incorrect proof... but for fucks sake understand why its incorrect...


Please allow me to re-iterate:
I FUCKING KNOW IT'S AN INVALID PROOF.

I divide by a(a - b) to *intentionally falsely* get that a = 2a, and thus 1 = 2.
a=b, so a-b=0, thus a(a-b) = 0, thus n / a(a / b) = infinite, thus at the part where I divide by a(a / b), I am dividing by fucking zero, thus you suck for not either understanding the joke or have a fucking sense of mathematical humour, funkyass.

In my equations, these are the only invalid parts:
(a(a - b)) / (a(a - b)) = (2a(a - b)) / (a(a - b))
1 = 2
But they are SUPPOSED to be invalid, because that's part of the practical joke. I.e. as DataPath has mentioned, "it's a classic "proof" to mess with the minds of people who enjoy math. ". The idea is that the person doesn't notice the division by zero, thus doesn't realize why it falsely comes that 1 = 2. So they think "wtf".
Call it "hidden in plain sight", or whatever, because that's the whole point of mathematical pranks such as this: hiding an error in plain sight to provide a false conclusion in order to fuck with people's minds.

Geez funkyass, you need to learn to lighten-up. This mathematically-correct stress is not good for you :P


Last edited by ZH/Franky on Mon Jan 12, 2009 10:05 pm, edited 2 times in total.



Mon Jan 12, 2009 9:57 pm
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I found my favourite one. It is much more subtle. No dividing by zero bullshit. No sir.
It's actually interesting to find where it fucks up. :)

x²+x+1 = 0
x² = -x-1

Now we set x != 0
x=-1-1/x

Substitute that in the first equation...
x² - 1 - 1/x +1 = 0
x² - 1/x = 0
x² = 1/x
x³ = 1
x = 1 != 0, ok...

Substitute that in the first equation again...
1² + 1 + 1 = 0
3 = 0

Have fun suckers

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Last edited by grinvader on Mon Jan 12, 2009 10:09 pm, edited 2 times in total.



Mon Jan 12, 2009 10:03 pm
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grinvader wrote:
I found my favourite one. It is much more subtle. No dividing by zero bullshit. No sir.
It's actually interesting to find where it fucks up. :)

Show me.
EDIT:
Ah, there it is. I'll take a look.
EDIT2:
I've been following that and seriously, the error must be quite subtle, with quite being an understatement. It'll take me a while to get this.


Last edited by ZH/Franky on Mon Jan 12, 2009 10:36 pm, edited 2 times in total.



Mon Jan 12, 2009 10:05 pm
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I like the "girls = evil" proof


Mon Jan 12, 2009 10:09 pm
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DataPath wrote:
I like the "girls = evil" proof

That one is actually lawlcorrect.

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Mon Jan 12, 2009 10:12 pm
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DataPath wrote:
I like the "girls = evil" proof

(there was something unrelated to this discussion previously here, but it was a lie; i was trying to test the "other people are gullible" theory)
HEY GRIN:
x² - 1/x = 0
is only true when x = 1At any other time (i.e. if x != 1), the fact that it's x^2 - the reciprocal of x (aka 1/x), then
(((x^2) - (1/x))) > 0

There's also the very fact that
x²+x+1 = 0 (your first equation)
is only true if x = 0 (you mention that x != 0, so immediately we know that the first equation is explicitly (and not implicitly) false.



So... what's the prize?


Last edited by ZH/Franky on Mon Jan 12, 2009 11:00 pm, edited 7 times in total.



Mon Jan 12, 2009 10:34 pm
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I forget how it goes, but there is an equation that 1.999(infinity) is equal to 2. Its probably common knowledge, but I always found it fascinating anyway.


Mon Jan 12, 2009 10:42 pm
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We should seriously make a thing of this "find the error" game :D


Mon Jan 12, 2009 11:02 pm
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Franky wrote:
x²+x+1 = 0 (your first equation)
is only true if x = 0 (you mention that x != 0, so immediately we know that the first equation is explicitly (and not implicitly) false.

Since when is 0²+0+1 = 0 ? Your prize is my finger at your face and nelson laughing in the background.

You only partially cornered the fallacy of the steps (you got a consequence, not the source). Try harder.

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Mon Jan 12, 2009 11:20 pm
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Quote:
2((a ^ 2) - ab) = 0
(a ^ 2) - ab = 2((a^2) - ab)


The second step is only true if a = b = 0. So in reality, all you have proved is 0=0.

There is no point to posting this whole thing. 1 does not equal 2. If you are freaking out about this, it is because you suck at math and logic.

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Mon Jan 12, 2009 11:24 pm
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badinsults wrote:
Quote:
2((a ^ 2) - ab) = 0
(a ^ 2) - ab = 2((a^2) - ab)


The second step is only true if a = b = 0. So in reality, all you have proved is 0=0.

There is no point to posting this whole thing. 1 does not equal 2. If you are freaking out about this, it is because you suck at math and logic.
Buh, I give up. Being mathematically correct is not the objective here. Being mathematically inconsistent is the objective (with the intention to confuse the person looking at the puzzle).

I do not suck at mathematics and logic.

grin wrote:
Since when is 0²+0+1 = 0 ? Your prize is my finger at your face and nelson laughing in the background.

You only partially cornered the fallacy of the steps (you got a consequence, not the source). Try harder.

...shit. Well, I'll dig further into it tomorrow (need sleep).
I honestly don't know how I figured that 0^2 + 0 + 1 = 0.


Last edited by ZH/Franky on Mon Jan 12, 2009 11:50 pm, edited 4 times in total.



Mon Jan 12, 2009 11:38 pm
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Franky wrote:
I do not suck at mathematics and logic.


this entire thread is proof to the contrary.

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Mon Jan 12, 2009 11:41 pm
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funkyass wrote:
Franky wrote:
I do not suck at mathematics and logic.


this entire thread is proof to the contrary.

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Tue Jan 13, 2009 2:13 am
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Deathlike2 wrote:
funkyass wrote:
Franky wrote:
I do not suck at mathematics and logic.


this entire thread is proof to the contrary.


Tue Jan 13, 2009 2:47 am
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h4tred wrote:
Deathlike2 wrote:
funkyass wrote:
Franky wrote:
I do not suck at mathematics and logic.


this entire thread is proof to the contrary.
am I doin it rite?

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Tue Jan 13, 2009 3:42 am
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http://www.anvari.org/fun/Gender/Proof_ ... _Evil.html

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grinvader wrote:
Now we set x != 0
x=-1-1/x


This step doesn't look right.

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