Root Expressions

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Akansha: Senior | Next Rank: 100 Posts; Posts: 56; Joined: Wed Sep 01, 2010 10:04 amFollowed by: 20 members; Thanked: 1 times

by Akansha » Sun May 29, 2011 10:36 am

x < 0, then âˆš-x |x| (root of the whole expression)
a. -x
b. -1
c. 1
d. X
e. âˆšx

OA is A. I got the answer as D. Can someone tell why is it not so? [/spoiler]

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Source: Beat The GMAT — Problem Solving | Sun May 29, 2011 10:36 am

sameerballani: Legendary Member; Posts: 544; Joined: Mon Dec 27, 2010 8:10 amFollowed by: 2 members; Thanked: 45 times

by sameerballani » Sun May 29, 2011 10:44 am

Akansha wrote:x < 0, then âˆš-x |x| (root of the whole expression)
a. -x
b. -1
c. 1
d. X
e. âˆšx

OA is [spoiler]A. I got the answer as D. Can someone tell why is it not so? [/spoiler]

Assume x = -4 (x<0)
Root[-x|x|]= Root[-(-4|-4|)]= Root[-(-4)*4]= Root[4*4]= 4 = -(-4)= -x = option A

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cans: Legendary Member; Posts: 1309; Joined: Mon Apr 04, 2011 5:34 amFollowed by: 123 members; Location: India; Thanked: 310 times; GMAT Score:750

by cans » Sun May 29, 2011 1:46 pm

âˆš-x |x| (root of the whole expression) should be +ve as there is no '-' sign in front of root.
and we know x<0
Thus D is not the answer.
and -X>0, also âˆš-x |x| = |x|
Thus A is the answer.

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