The Student Room Group

2=1 ?!?!?!

Explain:

a=b
a^2=ab
2a^2=a^2+ab
2a^2-2ab=a^2-ab
2(a^2-ab)=(a^2-ab)
2=1
?????


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Reply 1
a^2 - ab = 0 by a = b.
Reply 2
this is OLD AND DEAD!
Reply 3
Wow. You broke Maths. You are now the indisputed master of the universe. How does it feel? :rolleyes:
Reply 4
I'm amazed people never get tired of this.
You cannot divide by 0.

Using variables, it would work.

Using real numbers, it will not work.
lol i still love that proof even though it isn't really a proper proof it confuses people quite a bit - but it does show why you shouldn't divide by 0
Reply 7


TROLL
Reply 8
omg 1.9999999999999999999999999999999999999999 =2 omg
Reply 9
Original post by tamimi
omg 1.9999999999999999999999999999999999999999 =2 omg


No, it doesn't.
1.999.... = 2
Original post by Instincts_2012
You cannot divide by 0.

Using variables, it would work.

Using real numbers, it will not work.


I don't understand what you mean by 'using variables, it would work'. You can't divide by a variable which potentially takes the value of zero without branching your reasoning into "either <expression> = 0 or <everything from dividing by the expression onwards>".
Reply 11
Original post by Trollin
No, it doesn't.
1.999.... = 2


Reply 12
Original post by tamimi


Guilty as charged. But seriously, the pedantry of mathematicians knows no bounds :P
Reply 13
Original post by tamimi


1.9˙ 1. \dot{9} does equal 2 2

But what the OP has written is nonsense!
Reply 14
Original post by raheem94
1.9˙ 1. \dot{9} does equal 2 2

But what the OP has written is nonsense!


I know that is widely accepted but I just can't see it that way. Wouldn't it be true saying:

1.9˙=211.\dot{9} = 2 - \frac{1}{\infty}

That's just my thought. But then again, the infinity fraction tends to zero... However that doesn't mean it shouldn't be there.
(edited 11 years ago)
Reply 15
Original post by Micky76
I know that is widely accepted but I just can't see it that way. Wouldn't it be true saying:

1.9˙=211.\dot{9} = 2 - \frac{1}{\infty}

That's just my thought. But then again, the infinity fraction tends to zero... However that doesn't mean it shouldn't be there.


I can't say much about it.

Read this.
Original post by As_Dust_Dances_
You've just assumed a equals b and that's like saying c also equals d which isn't the case!


Lol what?
Original post by Slumpy
I'm amazed people never get tired of this.


because nobody stops for a second and thinks, they just get overwhelmed by the sheer plausibility and why nobody has seen it yet :tongue:
Trifling!
this doesn't work with 0 values a good example is 2x=x (/x) 2=1 2x-x=0 x=0.In the above proof a^2-ab=0 because it is equal to aa-aa=0 and 2 times that will equal 1 times that.

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