# Prove 3 + 4 = 8

AThousandYoung
Posers and Puzzles 18 Oct '04 20:34
1. AThousandYoung
All My Soldiers...
18 Oct '04 20:34
2. 21 Oct '04 16:09
4+4=8.

Then swap the 4 for a 3.
3. AThousandYoung
All My Soldiers...
22 Oct '04 04:20
Nope.
4. TheMaster37
Kupikupopo!
22 Oct '04 09:23
Using axioms of mathematics;

3+4 = 4+3 this is the communitative property of addition.
4+3 = 4+(2+1) this is the definition of 3
4+(2+1) = 4+(1+2)
4+(1+2) = (4+1) +2 this is the associative property of addition
(4+1) +2 = 5+2 this is the definition of 5
5+2 = 5+(1+1) this is the definition of 2
5+(1+1) = (5+1) +1
(5+1) +1 = 6+1 this is the definition of 6
6+1 = 7 this is the definition of 7

Proof above shows 3+4=7, nothing more, nothing less.

Now by assuming 0=1 or some other equivalent statement, it's easy to show 7=8, making 3+4=7=8. Alas, 3+4 would equal anything then.
5. AThousandYoung
All My Soldiers...
22 Oct '04 23:53
I still say 3 + 4 = 8, and I can prove it.
6. XanthosNZ
Cancerous Bus Crash
23 Oct '04 02:33
(3^2) - 21 = (4^2) - 28
9 - 21 + (35/4) = 16 - 28 + (35/4) Adding 35/4 to both sides
(3 - (7/2))*(3- (7/2)) = (4 - (7/2))*(4 - (7/2)) Factorising
(3 - (7/2)) = (4 - (7/2) Taking the square root of both sides
Therefore 3 = 4

Substituting into the equation 4 + 4 = 8
we get 4 + 3 = 8

How's that?
7. 23 Oct '04 07:11
gj Brother Edwin ur my hero ^.^
8. Ragnorak
23 Oct '04 14:301 edit
Originally posted by XanthosNZ
(3^2) - 21 = (4^2) - 28
9 - 21 + (35/4) = 16 - 28 + (35/4) Adding 35/4 to both sides
(3 - (7/2))*(3- (7/2)) = (4 - (7/2))*(4 - (7/2)) Factorising
(3 - (7/2)) = (4 - (7/2) Taking the square root of both sides
Therefore 3 = 4

Substit ...[text shortened]... ting into the equation 4 + 4 = 8
we get 4 + 3 = 8

How's that?
so that means that 3 + 3 = 8 as well??? And inversely, 4 + 4 = 6???

D
9. TheMaster37
Kupikupopo!
23 Oct '04 15:03
lets write 3-7/2 differently; -1/2

Name 1/2 = a. So 3-7/2 = -a

(-a)^2 = a^2

taking roots; -a = a

10. telerion
True X X Xian
23 Oct '04 16:291 edit
Originally posted by XanthosNZ
(3^2) - 21 = (4^2) - 28
9 - 21 + (35/4) = 16 - 28 + (35/4) Adding 35/4 to both sides
(3 - (7/2))*(3- (7/2)) = (4 - (7/2))*(4 - (7/2)) Factorising
(3 - (7/2)) = (4 - (7/2) Taking the square root of both sides
Therefore 3 = 4

Substit ...[text shortened]... ting into the equation 4 + 4 = 8
we get 4 + 3 = 8

How's that?
9 - 21 + (35/4) = 16 - 28 + (35/4) Adding 35/4 to both sides

(3 - (7/2))*(3- (7/2)) = (4 - (7/2))*(4 - (7/2)) Factorising

Uhm . . . you also have an arithmetic error.

(-7/2)*(-7/2) = 49/4

ok let's say you changed 35/4 to 49/4

you basically have (-1/2)*(-1/2) = (1/2)*(1/2) True.

but the next line is equivalent to -1/2 = 1/2 False.

Problem? sqrt(1/4) = 1/2 or -1/2
From this however we cannot say that 1/2 = -1/2

11. genius
Wayward Soul
23 Oct '04 17:44
Originally posted by TheMaster37
so, are you saying you can prove it without making any mathematical mistakes...? ðŸ˜›

12. XanthosNZ
Cancerous Bus Crash
23 Oct '04 21:47
(-7/2)*(-7/2) = 49/4
ok let's say you changed 35/4 to 49/4
you basically have (-1/2)*(-1/2) = (1/2)*(1/2) True.
but the next line is equivalent to -1/2 = 1/2 False.
Problem? sqrt(1/4) = 1/2 or -1/2
From this however we cannot say that 1/2 = -1/2
Yes you're right. It seems I can't multiply. You are also right in finding the flaw in the logic of my argument. Of course it's there. You don't actually think I can prove 3=4 without one do you? There is the more common 'proof' of 1=2 that uses dividing by zero.
Nice eyes spotting the mistake though. First time round it took me a while.
13. telerion
True X X Xian
23 Oct '04 22:37
Originally posted by XanthosNZ
Yes you're right. It seems I can't multiply. You are also right in finding the flaw in the logic of my argument. Of course it's there. You don't actually think I can prove 3=4 without one do you? There is the more common 'proof' of 1=2 that uses dividing by zero.
Nice eyes spotting the mistake though. First time round it took me a while.
Certainly, I didn't expect you to actually believe your proof. Good job thinking up the completing the square bit.
14. XanthosNZ
Cancerous Bus Crash
24 Oct '04 01:371 edit
I can't take full credit. It was first shown it by a math teacher years ago.
15. AThousandYoung
All My Soldiers...
25 Oct '04 00:161 edit
Wow Xanthos, that's pretty amazing. It's not the answer I was thinking of though.