Here is an interesting false proof as to how to multiply $2 \cdot  2$. Taken from [this  link][1].

   ![alt text][2]


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$\Large\textbf{Another example}$:



![alt text][3]


  [1]: http://math-fail.com/2011/09/what-is-2-x-2.html
  [2]: http://img.math-fail.com/wp-content/uploads/joke.png
  [3]: https://skullsinthestars.files.wordpress.com/2008/12/neg1equals1.png?w=640