The "2=1?" Answer

The fallacy begins in line 5. While it's surely ok to subtract 2b from both sides, and also to factor out (a-b), you have to realize something very important while you do. It was assumed that a=b in the very beginning, right? That means that a-b = none other than ZERO. And since multiplying any muber by ZERO renders ZERO, all this proof is really prooving is that 0=0.

2=1?

Original Via

Let's see.. How can this be? It appears quite valid that if you assume any two numbers are equal (a=b), that it has just been proven that 2=1. Clearly, 2 does not equal 1, so there must be a fallacy somewhere in this argument.

See if you can come up with it - I'll have the answer tomorrow.