I used to have three fallacious proofs that 1=0.

The first one was regarding infinite series:

0 = (1-1) + (1-1) + ...

= 1 + (-1 + 1) + (-1 + 1) + ...

ergo, 0=1

The second one was based on dividing by zero:

0 x 0 = 0

0 x 1 = 0

0 x 0 = 0 x 1

divide both sides by zero

0/0 x 0 = 0/0 x 1

ergo 0=1

The last one, I forgot, it was integral based. Anyone have any ideas which it was?