BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

numbers

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 208
Joined: Sun Sep 28, 2008 12:30 pm
Thanked: 22 times

by neoreaves » Sat Apr 10, 2010 11:28 pm
Ans = -x


This is a positive\negative question. So GMAT will trick you with positive and negatives.

Now we know that x < 0 ....that means -x >0 .....e.g. -1 , -2 and so on

|x| is the absolute value of x = positive value of x
-x is also the positive value of x

Thus -x|x| gives us x ^2 ...which is positive

we take the sqrt of -x|x| and we get back x .....WRONG

we dont get x back ...we get -x back because sqrt gave us back the positive version of x ..which was -x

Thus that should be the answer
Top
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 am
Thanked: 137 times
Followed by:5 members

by thephoenix » Sat Apr 10, 2010 11:48 pm
suppose x=-1
then -x*lxl=-(-1)*l-1l=1*1=1
we assumed x=-1 and we are getting value 1 which is nothing but -x(bcoz x is -1)
hence value for the expression is -x
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 270
Joined: Wed Apr 07, 2010 9:00 am
Thanked: 24 times
Followed by:2 members

by neerajkumar1_1 » Sun Apr 11, 2010 12:21 am
Thanks guyz...
Top
User avatar
Legendary Member
Posts: 1022
Joined: Mon Jul 20, 2009 11:49 pm
Location: Gandhinagar
Thanked: 41 times
Followed by:2 members

by shashank.ism » Sun Apr 11, 2010 10:55 pm
neerajkumar1_1 wrote:if x<0, then sqrt(-x*|x|) is ?
since x<0 so |x| = -x
--> sqrt(-x*|x|) = sqrt(-x*-x) = sqrt(x2) = |x| = -x (since x<0)
My Websites:
www.mba.webmaggu.com - India's social Network for MBA Aspirants

www.deal.webmaggu.com -India's online discount, coupon, free stuff informer.

www.dictionary.webmaggu.com - A compact free online dictionary with images.

Nothing is Impossible, even Impossible says I'm possible.
Top
Post new topic Post Reply
• Page 1 of 1