Mathematics

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The equality x-x=0 and 0=x-x are suppose to be the same. The first equality is easy to understand while the second equality( 0=x-x )is somewhat mind boggling to me for the following reason: where do the 2x's on the right side come from?
Thanks
Kal
Accepted:April 26, 2012

Accepted:

April 26, 2012