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singh21: Junior | Next Rank: 30 Posts; Posts: 15; Joined: Sat Jul 05, 2008 6:19 pm; GMAT Score:710

by singh21 » Wed Mar 18, 2009 2:42 pm

Can anyone explain this? I may be missing something here....Thanks!!!

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Source: Beat The GMAT — Problem Solving | Wed Mar 18, 2009 2:42 pm

cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Wed Mar 18, 2009 2:50 pm

Singh,

I am sure that this has been explained before on this forum atleast a few times but here it goes. Please use the search option if possible. This way u dont have to wait on a response since they have been answered already(saves u time).

sqrt( -x |x|)

Definition of modulus

|x| = x if x>=0

|x| = -x if x<0

In the given problem x is negative

Applying the defnition here |x| = -x

sqrt(-x * -x) = sqrt(x^2) = +ve x

So this +ve x is - (original x which is negative)

So -x is the answer.

Regards,
CR

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singh21: Junior | Next Rank: 30 Posts; Posts: 15; Joined: Sat Jul 05, 2008 6:19 pm; GMAT Score:710

by singh21 » Wed Mar 18, 2009 3:22 pm

Thanks Cramya !!! Looking at the question, it never occurred to me that GMAT can trick you on such so called obvious questions

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kaf: Senior | Next Rank: 100 Posts; Posts: 53; Joined: Mon Feb 09, 2009 12:18 am; Thanked: 1 times

by kaf » Thu Mar 19, 2009 12:55 am

cramya

could you please explain definition of modulus and generally the whole process

sqrt( -x |x|)

Definition of modulus

|x| = x if x>=0

|x| = -x if x<0

In the given problem x is negative

Applying the defnition here |x| = -x

sqrt(-x * -x) = sqrt(x^2) = +ve x

So this +ve x is - (original x which is negative)

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