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- January 26th 2010, 11:38 AM #1

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- Mar 2009
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## 2=1 ?

Hello,

I have a question regarding a problem that my prof gave me:

x=y

then

x² = xy

x²- y²= xy- y²

(x-y) (x+y) = (x-y) y

x+y= y

y+y=y

2y=y

which would mean that 2=1

Can someone**explain**me where the problem is?

Thanks in adavance!

- January 26th 2010, 11:40 AM #2

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- January 26th 2010, 11:40 AM #3

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Mathematical fallacy - Wikipedia, the free encyclopedia

Scroll to Division by zero for your question.

- January 26th 2010, 11:41 AM #4

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