Bert blogt

Today, while I was browsing the web I encountered this piece of math:

       a = b
   a + a = a + b
      2a = a + b
 2a - 2b = a + b - 2b
2(a - b) = a + b - 2b
2(a - b) = a - b
       2 = 1

On first sight you might think it is correct, but if you look a little bit closer you can easily see the error!
let’s try it again:

       a = b            //true
   a + a = a + b        //true
      2a = a + b        //true
 2a - 2b = a + b - 2b   //true
2(a - b) = a + b - 2b   //true
2(a - b) = a - b        //true <=> 2a - 2b = a - b <=> a - b = a - b <=> 0 = 0
       2 = 1            //false (should be 0 = 0)

that’s it for my ranting =)