hi folks.. on Kaplan prep guide I found he following explanation for Sq roots on GMAT. But in real maths it is DIFFERENT! The Sq Root has always two values: + and - It is very ambiguous! May be it is typo on Kaplan method.....

i would go with what GMAT considers correct, simply because the GMAC is who ultimately decides your score.

Hope I am not mistaken here. This is what is called the principal square root of a real number ( i.e. non negative square root of a real number). I think this is what we mean when we say square root in the math world and GMAT.

so, according to GMAC, the OA for the next question must be D right?

It may sound a bit confusing. This is what my understanding is When I say square root what I mean is let say sqrt(16) = ? We use +4 since if u consider 16 as (-4)^2 or (4)^2 sqrt(x^2) = |x| If u take x=-4 or +4 u still get the square root as +4 only because u r taking the absolute value In the problem above a^2 = 4 sqrt(a^2) = sqrt(2) ^ 2 or sqrt(a^2) = sqrt(-2) ^ 2 |a| = 2 (since |2| or |-2| is 2) Whenever u have modulus u have 2 cases when its positive and negative (nothing to do with square root since u have crossed that stage above) so a=2 (or) -a=2 i.e a=-2 2 possible values I hope I made sense here! Someone please feel free to jump in and correct me if I am mistaken.

here's the deal: you're talking about two different things. when you have an OPERATOR SYMBOL, such as "√", that symbol will produce exactly ONE value. for instance, √9 is just 3. |-5| is just 5. and so on. notice, in these cases, that you're merely simplifying expressions; you are NOT solving EQUATIONS. in other words, there's no "=" sign in the middle of what you're dealing with; you're not finding the solutions of anything. just simplifying. when you solve an EQUATION, there may well be more than one solution. if you say x^2 = 9, there are two solutions: x = 3 and x = -3. notice that i can say this without speaking of the "√" symbol at all! indeed, the "√" symbol is DEFINED to refer only to the positive root. it is NOT defined to refer to either of the 2 solutions to the above equation. hth.

Cramya, next time you thank Lunarpower, you can also try to click THANK YOU button. ( I have not been teasing you for a while so live with it) And also who is the ONLY person you thanked ? And what was it for ?hahahaha

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