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If X < 0 , then SQRT ( ( -x) * |x| ) is equal to?

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kourakis
 Post subject: If X < 0 , then SQRT ( ( -x) * |x| ) is equal to?
 Post Posted: Sun Aug 21, 2011 5:54 pm 
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Students


Posts: 8
If X < 0 , then SQRT ( ( -x) * |x| ) is equal to?

-x , -1, 1, x, SQRTX

Apologies if this has already been posted.

OA is -x. I would say it is X (shouldn't it be |x|?), because a square root is always positive (x^2=4 -- x=+/- 2, but SQRT4 = 2)

Please advise. Thanks!
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mithunsam
 Post subject: Re: If X < 0 , then SQRT ( ( -x) * |x| ) is equal to?
 Post Posted: Sun Aug 21, 2011 7:35 pm 
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Course Students


Posts: 76
It should be -x.

sqrt(-x *|x|) = sqrt(x * x) --> (Since x < 0, -x = +x. Also, |x| = x)
=sqrt(x^2) =+ x

Now we have to choose between +x and -x. Since x<0, +x will be -ve and -x will be +ve. For sqrt of a number, we have to choose +ve root. Therefore, -x is the correct answer.
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RonPurewal
 Post subject: Re: If X < 0 , then SQRT ( ( -x) * |x| ) is equal to?
 Post Posted: Thu Aug 25, 2011 4:14 am 
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ManhattanGMAT Staff


Posts: 7146
please search the forums, people

if-x-0-then-sqrt-x-x-is-t903.html

if you have any further questions about this problem, please post them on that thread; this thread will now be locked. (please read the whole thread before you post a question!)
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