The Plastic Brain

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As Ned Flanders would say: 

 

Oh, That’s A Noodle-scratcher.

I must admit defeat. Though I followed all the reasoning, I couldn’t find the flaw.

I had to look it up on, of all places, Wikipedia.

Answer and link below the quote….

“Via scienceisbeauty:

This problem! From Calculus By Michael Spivak we suffer on first course. I’ve used it many times and few people are right, even people of sciences. Though I suppose this will be very  easy for many of you. For others don’t, of course. That is the funny.

Clue: two is not one, definitely. You all know it!”

The flaw arises when moving from line 3 to 4, ie divide by (x-y).

Can’t be done, because if x=y then that’s the same as dividing by zero, which is a big no-no.

See: http://en.wikipedia.org/wiki/Mathematical_fallacy

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Author: Rogan Tinsley

Biology, science and maths teacher with a PhD in Neuroscience and passion for education.

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