Quote:
Originally Posted by joepole
Actually, step 3 is fine, the distributive property was used correctly.
The problem is that between 3 and 4 you divide both sides by (a + b - c) which, according to the initial equation, is 0. You can't divide by 0.
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Yes, the distributive property was used correctly, but it shouldn't have been used at all. Combining like terms is a fundamental of algebra and the author avoided it entirely in order to get the outcome that he did.
Go to
http://www.algebrahelp.com/calculators/equation/ and run the equation from step 2 and you'll see what I mean.
Improper calculation = invalid outcome!