# 1=2 ?

1. Dec 11, 2006

### Tido611

I was once shown a cool little trick that "proved" 1=2 and i was wondering if anyone knew what it was or where i could find it, thanks.

2. Dec 11, 2006

### neutrino

I just typed 1 = 2 in the Wikipedia search box and it led me to the page for 'Invalid Proofs'. You might also want to google it.

3. Dec 11, 2006

### matt grime

There a thousands of 'em, all relying on the fact that dividing by 0 is not allowed. Just devise your own.

4. Dec 11, 2006

### Kurdt

Staff Emeritus
5. Dec 11, 2006

### Gib Z

$$x^2 - x^2 = x^2 - x^2$$

$$x(x-x)=(x-x)(x+x)$$ Supposedly, the (x-x)'s cancel out, though it equals zero so you cant divide by it.

$$x= x+x$$

In other words, 1=2

6. Dec 12, 2006

### EmilK

I generally despise such tricks, because as mentioned above, once you see one, you have pretty much seen them all. There are apparently over 36 million hits on Google using the term '"1=2" proof'. You could always spend the time on other things in mathematics than this :tongue2:

7. Dec 13, 2006

### Leopold Infeld

Oh, come on, u dont need to despise them. It could be of great benefit to kids out there who for their first time had seen something unusual. This might inspire them to become the next person to solve riemann's conjecture or unifry all forces of nature. Just like Andrew Wiles who was inspired during his youth to solve FLT.

I first saw this 1=2 business when i was 15, amazed me to no end and made my interest in maths grew even more . haha