Q&A #19812

Explaining concept -x=2 is equal to x=-2

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From: Gail (for Teacher2Teacher Service)
Date: Oct 25, 2008 at 07:44:33
Subject: Re: Explaining concept -x=2 is equal to x=-2

Hi Sam, Has your class talked about coefficients? I think the key here is that -x really has a coefficient of -1. So, if you want "the x all by itself", you have to divide both sides by -1, and you have -x = 2 __ __ -1 -1 and that simplifies to x = 2/-1, or -2 another way to look at it is using the idea of opposites, which is what I teach my students. that - means "the opposite of", so -x means "the opposite of x. If the opposite of x is 2, then x must be -2. Hope this gives you someplace to start... :-) -Gail, for the T2T service

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