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Equations, Inequalities and VICs, Chapter 4, Question 3

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nvingers
 Post subject: Equations, Inequalities and VICs, Chapter 4, Question 3
 Post Posted: Thu Jan 22, 2009 1:27 am 
The answer to question 3 states that the solution for (A + B)^2 = 9 could be BOTH 3 and -3. The In Action Answer Key specficially advises that both "positive and negative" roots should be "taken into account." This seems odd, since the Manhattan GMAT Strategy Guide on Number Properties (3rd edition) explicitly states (in Chapter 6, p. 113) that "the GMAT follows the standard convention that when we are taken an even root [...], a radical (root) sign denotes only the nonnegative root of a number."

Could somebody explain to me what's going on here?
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JonathanSchneider
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 Post Posted: Thu Jan 22, 2009 5:37 pm 
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ManhattanGMAT Staff


Posts: 380
Good question. Whenever you see an even exponent, be on the lookout for negative solutions. HOWEVER, when the test already gives you the square root sign, you do not have to consider any negative solutions. The square root sign, by definition, means positive only. This is not the case however when you take the square root of a number yourself, only when the GMAT has already done it for you.
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Guest
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 Post Posted: Fri Jan 23, 2009 11:09 pm 
ok, got it... thanks for clarifying!! :)
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JonathanSchneider
 Post subject: Re: Equations, Inequalities and VICs, Chapter 4, Question 3
 Post Posted: Wed Feb 11, 2009 12:52 pm 
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Posts: 480
Location: Durham, NC
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