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-- A Weird Math Problem ....


Posted by King_Mack on Jan-30-2004 05:51:

Rasta A Weird Math Problem ....

Im trying to prove to my friend that what he's saying makes no sense. In any case, here's the argument...can someone refute it?


Read:- 'a2' below as "a squared," 'b2' below as "b squared," etc.

If a = b (so I say) [a = b]
And we multiply both sides by a
Then we'll see that a2 [a2 = ab]
When with ab compared
Are the same. Remove b2. OK? [a2-b2 = ab-b2]

Both sides we will factorize. See?
Now each side contains a - b. [(a+b)(a-b) = b(a-b)]
We'll divide through by a
Minus b and ol�

a + b = b. Oh whoopee! [a+b = b]
But since I said a = b
b + b = b you'll agree? [b+b = b]


So if b = 1
Then this sum I have done [1+1 = 1]
Proves that 2 = 1. Q.E.D.


good luck I only argued on grounds that he keeps assuming shit hehe but that argument aint good enough..


Posted by mmilo on Jan-30-2004 06:03:

if a=b,
then a-b=0
and you cannot divide by zero.


Posted by King_Mack on Jan-30-2004 06:08:

Rasta

i took that approach, but he's not too impressed by that hrm...

is there anything else you can see that flaws from what he presented? I mean..from first glance, it seems mathematically correct(his induction)....but theres something in there that doesnt make sens. I cant put my finger on it though, unless the only thign is the division issue..


Posted by {b.s.e.} on Jan-30-2004 06:16:

I think your problem is right here: Remove b2. OK? [a2-b2 = ab-b2]

I don't even know where b^2 comes from. We have a^2, as well as ab. Even if you had b^2 you cannot subtract that from ab since they are not like terms. I think you need to make substitutions so that your algerbra is suitable. But of course, once you make subs, everything will equal zero and will render your equation void.

I hate math, I'm going to play some chess.


Posted by Perfect_Cheezit on Jan-30-2004 06:20:

just wait for Noisician, he'll set things straight


Posted by _Nut_ on Jan-30-2004 06:22:

(original eq)
a = b
(both sides mult through by a)
a^2 = ab

When with ab compared
a = b
ab = b^2

Are the same. Remove b2. OK? [a2-b2 = ab-b2]


a^2 = ab = b^2
(division to remove the middle term)
a/b = 0 = b/a

where a/b = -b/a
then
a^2/b = -b

a^2 = -1

therefore

a = sqrt(i) [you cannot take the sqrt of negative nums so you have to bust out the imaginary numbers algebra]




you were coming up with some odd shit. saying things factored and all that. following through the begining this is what i computed. Are you trying make up some theorum of sorts? if you are you need to lay off the green.


Posted by DasBrotBesser on Jan-30-2004 06:40:

you're forgetting that ab=a^2=b^2 since a=b

hence it should be a^2=ab=B^2
remove b^2
therefore a^2-b^2=b^2-b^2=0

but even without that, a-b=0, so then it would be
(a+b)(0)=b(0)=0

so then your last equation would be 0=0


Posted by DrUg_Tit0 on Jan-30-2004 12:12:

Re: A Weird Math Problem ....

quote:
Originally posted by King_Mack

Now each side contains a - b. [(a+b)(a-b) = b(a-b)]
We'll divide through by a
Minus b and ol�


As mmilo said earlier, the division by 0 is where the flaw lies. First you have (a+b)*0=b*0=0, and so far the argument is a correct one. But after the division, you basically get (a+b)*0/0=b*0/0 which is not defined because 0/0 can be equal to anything.


Posted by Flyboy217 on Jan-30-2004 22:12:

quote:
Originally posted by King_Mack
i took that approach, but he's not too impressed by that hrm...

is there anything else you can see that flaws from what he presented? I mean..from first glance, it seems mathematically correct(his induction)....but theres something in there that doesnt make sens. I cant put my finger on it though, unless the only thign is the division issue..


This explanation is correct. Dividing by zero invalidates the equation. Your friend's "proof" belongs to a whole class of such spurious explanations of false equalities.


Posted by whiskers on Jan-30-2004 22:30:

Re: Re: A Weird Math Problem ....

quote:
Originally posted by DrUg_Tit0
As mmilo said earlier, the division by 0 is where the flaw lies. First you have (a+b)*0=b*0=0, and so far the argument is a correct one. But after the division, you basically get (a+b)*0/0=b*0/0 which is not defined because 0/0 can be equal to anything.



i confirm that too, there are a bunch of problems in computer & math textbooks that rely on this "division by 0" approach to have you find the error in the algorithm.


Posted by zarathustra on Jan-31-2004 02:58:

Division by zero is illegal.


Posted by astroboy on Jan-31-2004 03:06:

quote:
Originally posted by King_Mack
i took that approach, but he's not too impressed by that hrm...


Impressed or not, you simply CAN NOT divide by zero. As soon as he does that his proof becomes invalid.


Posted by smokeape on Jan-31-2004 03:48:

How much ramming speed do I need?



[[[smoke]]]


Posted by Fast Turtle on Jan-31-2004 04:56:

Straight from my computer logic text book:

""Proof" of 2 = 1"
step
1.) a = b
2.) a^2 = ab
3.) a^2-b^2=ab-b^2
4.) (a-b)(a+b)=b(a-b)
5.) a+b=b
6.) 2b = b
7.) 2 = 1

Fallacy: Every step is valid except for step 5, where we divided by a-b. a-b = a-a or b-b = 0, so we divided by zero, which is impossible.

As stated before. Famous invalid proof.



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