You can make 1 = 2... Wrong

A few people may have seen this video: http://www.youtube.com/watch?v=cqj5Qrxd5M0

Just to clear it up, you cannot make 1 = 2!

The working is as follows...

a = b

a + a = b + a

2a = b + a

2a - 2b = b + a - 2b

2(a - b) = a - b ---> (it's still correct here...)

Now the idiot that wrote this working claims that you can divide both sides by (a -b), and be left with 2 = 1.

Ok great, what he failed to mention is that if a = b, a - b must equal 0. This means he is saying (2(0))/0 = (0)/(0). You can't divide by zero so this is invalid math.

I'm sure a few people's hearts skipped a beat when they first saw this though. :)