Proof that 4 equals 3

Begin with a simple algebraic equation:
a + b = c

Now, replace each letter with 4 of that letter minus 3 of that letter:
4a - 3a + 4b - 3b = 4c - 3c

Rearrange, so that the 4s are on the left and the 3s on the right
4a + 4b - 4c = 3a + 3b - 3c

Simplify by factoring:
4(a + b - c) = 3(a + b - c)

Then divide each side by a+b-c:
4 = 3


There is, of course, a fallacy in this process. I invite someone to point out the defect with an appropriate comment in the "comments" section.

[This is an old post from 2007; I'm conducting a test to see if the Blogspot host will allow me to move this to a current position and still leave the comments attached. Then I'll try to move it back. Please ignore.]