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Square Roots

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by cris » Thu Jan 24, 2008 3:55 pm
I have always thought that when GMAT gives you a Square Root....it only has one possible answer, and hat is its positive solution (the negative solution is not taken on account).

So I am having problems understanding thid problem:

What is the value of x?

1) Squareroot(x^4)=9

2) The average of x, 6x, and 3 is -2

Statement 2 is SUFF.

But what about statement 1? One would think that "Squareroot(x^4)=9" is the same has saying "x^2=9" so x has two possible answers: +3 and -3. BUT I thought that when GMAT writes "Squareroot" it is only refering to the positive value of the root...that is +3.....So I chose D, but the correct answer is B because it says that satement 1 gives two possible answer (+3 and -3).

Can someone please explain me if its true or not that when GMAT gives us a Squareroot it only has one possible answer (the positive value)??

Thanks! :shock: I am bit confused...
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Source: — Data Sufficiency |

by gmatguy16 » Thu Jan 24, 2008 5:49 pm
chris,
sq rt(x ^ 4) =9 in which case x ^ 2 = 3. hence value of x could be
+ or -ve (sq rt 3) thats why a is not sufficient.
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by cris » Fri Jan 25, 2008 7:07 am
Yes I know that, the thing is that when GMAT writes "squareroot" its only refering to the positive value...that is my question... :?:
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by sankruth » Fri Jan 25, 2008 8:25 am
Look at it this way...

Lets say, x^4 = y

sqrt(y) = 9

So, y = 81 = x^4

So x can be +3 or -3
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