Teacher2Teacher 
Q&A #19812 
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From: Robert To: Teacher2Teacher Public Discussion Date: 2009090615:07:55 Subject: x=2 is equal to x=2 Here is another idea. Take the equation x=2 and add to it the equation x=  2. On the left the x's cancel: on the right the 2's cancel. Hence 0 = 0. Therefore, the equations are true. If the equations are true, it follows that 1 times  1 = +1 and a negative times a negative must result in a positive. I append the thought: Mental shortcuts may lead to mental traps." The FAQ Ogden Nash quotation is worth repetition:" Negative times negative results in a plus/The reasons for this we need not discuss." Robert
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