Math Fallacy Proofs

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. 
\(a = b\)
\(a^2 = ab\)
\(a^2  b^2 = abb^2\)
\((ab)(a+b) = b(ab)\)
\(a+b = b\)
\(b+b = b\)
\(2b = b\)
\(2 = 1\)The whole fallacy proof went wrong (or became right, depending on which angle you look at it) when you divide by \(ab\), which is \(0\)!

$$0=(11)+(11)+(11)+(11)\cdots$$ $$0=11+11+11+11+\cdots$$ $$0=1+(1+1)+(1+1)+(1+1)+\cdots$$ $$0=1+0+0+0+\cdots$$ $$0=1$$