Math Fallacy Proofs

RZ923

There are many fallacy proofs in maths so you can share some for fun!
You can also write why the fallacy proof is a fallacy proof.

RZ923

$a = b$
$a^2 = ab$
$a^2 - b^2 = ab-b^2$
$(a-b)(a+b) = b(a-b)$
$a+b = b$
$b+b = b$
$2b = b$
$2 = 1$

The whole fallacy proof went wrong (or became right, depending on which angle you look at it) when you divide by $a-b$, which is $0$!

tidyboar

$$0=(1-1)+(1-1)+(1-1)+(1-1)\cdots$$ $$0=1-1+1-1+1-1+1-1+\cdots$$ $$0=1+(-1+1)+(-1+1)+(-1+1)+\cdots$$ $$0=1+0+0+0+\cdots$$ $$0=1$$