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Q&A #4168

Teachers' Lounge Discussion: Algebra

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From: Arthur Minor <minor_a@popmail.firn.edu>
To: Teacher2Teacher Public Discussion
Date: 2001121021:19:27
Subject: Re: Algebra


Proof of 2 = 1


Let a = 1

Multiply by a to get a^2 = a

Subtract 1 to get a^2 - 1 = a - 1

Factor left side (difference of two squares) to get

(a + 1)(a - 1) = a-1

Divide both sides by a-1 to get a + 1 = 1

Sustitute 1 for a to get 1 + 1 = 1 so 2 = 1

The fallacy is we divided a-1/a-1 = 1, but it is really 0/0 undefined.

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