2+2=5

2+2=5

Posers and Puzzles

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F

Joined
11 Nov 05
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43938
16 Sep 07

The funny thing with the decimal positional system is that you can often (not always) write the same number in two ways.

0.99999... = 1
0.2499999... = 0.25
etc.

This is not a flaw, it is a property.

m

Joined
07 Sep 05
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35068
16 Sep 07

Originally posted by EinsteinMind
This convention will not work when x is any negative integer. for instance, the two square roots of -1 are indeed i and -i. These cannot be distinguished on the basis of "positive" and "negative"; so how do we know which one is being meant by SQRT -1?

Therefore this step of the proof may seem unclear.

HOwever, this can be easily remedied.

Just ...[text shortened]... ative multiple of i."

It simply rationalizes away by defining which SQRT you are after.
But by rationalising it away you've changed the definition of SQRT to such an extent that the step 2->3 is no longer valid.

r

Tony, kiss mine!

Joined
18 Mar 06
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3118
16 Sep 07

Originally posted by doodinthemood
This is generally to do with rounding:
2.4 rounds to 2
2.4+2.4=4.8 which rounds to 5.

If you round everything: 2+2=5
premature rounding not allowed in mathematics and is not given any credit on AP Exams

S
Caninus Interruptus

2014.05.01

Joined
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92274
16 Sep 07

Originally posted by rubberjaw30
premature rounding not allowed in mathematics and is not given any credit on AP Exams
premature jocularity not allowed around math dorks and is not recognized as humor due to substandard social conditioning

j

Joined
14 Jun 07
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1417
18 Sep 07

Originally posted by Doctor Rat
If there is a general formula involved in the proof, make sure division by zero isn't happening because that isn't allowed. So for example the classic case of the fallacy of 1=2 (which is very similar to yours)
step 1
[b]Let a = b

step 2 Multiply both sides by a:
aa = ab
step 3 which is the same as:
a^2 = ...[text shortened]... oof of 2+2=5.

(sorry for all the edits, but I had to work out some formatting issues)
i'm seriously confused now...

DR

Joined
02 Jul 07
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2416
18 Sep 07

Originally posted by jenna1
i'm seriously confused now...
Go with your instincts, Jenna1.

T

Joined
17 Sep 07
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5081
18 Sep 07
2 edits

step 1
Let a = b
step 2 Multiply both sides by a:
aa = ab
step 3 which is the same as:
a^2 = ab ( "a squared equals a times b" )
step 4 Add the quantity ( a^2 - 2ab) to both sides:
a^2 + (a^2 - 2ab) = ab + (a^2 - 2ab)
step 5 simplifying both sides we get:
(a^2 + a^2) - 2ab = a^2 + (ab - 2ab)
2(a^2) - 2ab = a^2 - ab
2 (a^2 - ab) = a^2 - ab
step 6 divide both sides by (a^2 - ab):
2(a^2 ...[text shortened]... ab) / (a^2 - ab) = (a^2 - ab) / (a^2 -ab)
step 7 cancel out like terms in num.&denom:
2 = 1 !!!
a^2 = ab
then is a^2-ab = 0
devide by 0 is not allowed

s
Astrophysicist

Outer Space

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46548
18 Sep 07

Originally posted by EinsteinMind
Wrong. It's a mistake, but an asusmption or a definition of which SQRT you are after, and the problem continues.
But you are creating exactly this kind of ambiguity.

1) -1 = -1 check
2) sqrt(-1) = sqrt(-1) check (providing your rule)
3) ambiguity inserts itself....
4) i / 1 = 1 / i is i = -i wrong!

l

Milton Keynes, UK

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80363
18 Sep 07
2 edits

Originally posted by eatmybishop
tell me in what way that is wrong and i'll back down.... i sense you know you've lost....

here's the quote on binary numeral system...

could you actually read the whole thread then get back to me... if you have trouble understanding it send me a message and i'll explain it to you...

it is them who have converted the answer to decimal... 10 + 10 ur; it is not, its value remains 10"

is this wrong too????

apology accepted loser
You will find that computers wouldn't convert to decimal, do the addition, and then convert back to binary. Decimal is only for us to easily understand, which is base 10 (ten) numbers. Binary are base two numbers which is what computers do arithmetic in because it can only handle two states.

Therefore, as far as computers is concerned, 1 + 1 = 0 (with 1 as a carry bit). Effectively meaning 01 + 01 = 10.

So if you were to do any addition in binary, it is quite correct to say 1 + 1 = 10. Same as saying 9 + 1 = 10 (decimal or base ten), or 7 + 1 = 10 (octal or base 8).

EDIT: What you are referring to is boolean algebra where "+" is representing the logic AND, which is something completely different.

0 AND 0 = 0
1 AND 0 = 0
0 AND 1 = 0
1 AND 1 = 1

e

Joined
29 Jan 07
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20 Sep 07

Originally posted by lausey
You will find that computers wouldn't convert to decimal, do the addition, and then convert back to binary. Decimal is only for us to easily understand, which is base 10 (ten) numbers. Binary are base two numbers which is what computers do arithmetic in because it can only handle two states.

Therefore, as far as computers is concerned, 1 + 1 = 0 (wi ...[text shortened]... hich is something completely different.

0 AND 0 = 0
1 AND 0 = 0
0 AND 1 = 0
1 AND 1 = 1
it was actually me who said a computer will not convert to decimal... they were saying it would....

with all respect, your boolean algebra is incorrect.. it should read...

0 + 0 = 0
1 + 0 = 1
0 + 1 = 1
1 + 1 = 1

hope this helps

P
Upward Spiral

Halfway

Joined
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8702
20 Sep 07

Originally posted by eatmybishop
your boolean algebra is incorrect..
Wrong.

e

Joined
29 Jan 07
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20 Sep 07
1 edit

Originally posted by Palynka
Wrong.
not if its a or operation (+) it isnt

example:

OR Operations (+)

0+0 = 0 A+0 = A
1+0 = 1 A+1 = 1
0+1 = 1 A+A = A
1+1 = 1 A+A' = 1

apology accepted... loser

e

Joined
29 Jan 07
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20 Sep 07

bet you wanna go hide now mr panda killer

S
Caninus Interruptus

2014.05.01

Joined
11 Apr 07
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92274
20 Sep 07

Originally posted by eatmybishop
it was actually me who said a computer will not convert to decimal... they were saying it would....

with all respect, your boolean algebra is incorrect.. it should read...

0 + 0 = 0
1 + 0 = 1
0 + 1 = 1
1 + 1 = 1

hope this helps
Everything you post about binary is wrong. Just stop.

e

Joined
29 Jan 07
Moves
3612
20 Sep 07

Originally posted by SwissGambit
Everything you post about binary is wrong. Just stop.
if its based on or operations its right... please tell me where that is wrong