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It's called mathematical fallacy. To go from (a+b)(a-b)=b(a-b) to a+b=b you must divide by (a-b) but because a=1 and b=1, a-b=0 and dividing by 0 is indeterminate. If we were able to divide by 0 then I could just as easily say 1/0=2/0 so 1=2

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This discussion board is a place to discuss our Daily Challenges and the math and science related to those challenges. Explanations are more than just a solution — they should explain the steps and thinking strategies that you used to obtain the solution. Comments should further the discussion of math and science.

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## Comments

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TopNewestSigh. This post has been posted way too much...just stop.

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well obviously, 2=2 so your theory kinda goes down the drain.

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It's called mathematical fallacy. To go from (a+b)(a-b)=b(a-b) to a+b=b you must divide by (a-b) but because a=1 and b=1, a-b=0 and dividing by 0 is indeterminate. If we were able to divide by 0 then I could just as easily say 1/0=2/0 so 1=2

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1/0 is not equal to 2/0

(sean S. is Right )

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a-b=0 , old joke

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Mathametic fallacy derp....you cant cancel out zeroes in an eqn..

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STOP DIVIDING BY ZERO. IT IS ILLEGAL IN MATH FOR A REASON.

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nice

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in your proof, $(a-b)=(1-1)=0$ and you can't divide by 0

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