Is X^2 greater than X ?

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California4jx: Master | Next Rank: 500 Posts; Posts: 227; Joined: Thu Aug 14, 2008 10:43 amFollowed by: 1 member; Thanked: 7 times; GMAT Score:650

by California4jx » Thu Jun 18, 2009 10:03 am

Is X^2 greater than X ?

(1) x^2 is greater than 1
(2) x is greater than -1

I need help understanding the part 1. if x^2 > 1 then i know that x > 1 or x > -1 but how come x could be x < -1 ??

thanks. OA later.

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Source: Beat The GMAT — Data Sufficiency | Thu Jun 18, 2009 10:03 am

shashank.mehra: Junior | Next Rank: 30 Posts; Posts: 12; Joined: Mon Jun 15, 2009 8:59 pm

Re: Is X^2 greater than X ?

by shashank.mehra » Thu Jun 18, 2009 10:13 am

California4jx wrote:Is X^2 greater than X ?

(1) x^2 is greater than 1
(2) x is greater than -1

I need help understanding the part 1. if x^2 > 1 then i know that x > 1 or x > -1 but how come x could be x < -1 ??

thanks. OA later.

IMO A.

Statement 1) x<-1 or x>1. Therefore in both the cases X ^ 2 > X

Statement 2) -1<x, therefore x can be a -ve or a positive fraction and hence can be greater or less than x ^2 respectively. So no answer

Therefore A.

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hk: MBA Student; Posts: 532; Joined: Wed Jan 28, 2009 1:39 pmFollowed by: 9 members; Location: Barcelona; Thanked: 33 times; GMAT Score:640

by hk » Thu Jun 18, 2009 12:01 pm

I will go with A.

1. Says that x cannot be a fraction, 0, 1, -1. For all other values of x, x^2 is greater than x. - sufficient.
2. x>-1, here x can be, say, 1 in which case x^2 = x or x can be 10 in which case x^2 is greater than x - Insufficient.

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mehravikas: Legendary Member; Posts: 1161; Joined: Mon May 12, 2008 2:52 amFollowed by: 1 member; Location: Sydney; Thanked: 23 times

by mehravikas » Thu Jun 18, 2009 5:56 pm

IMO - A

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electrico: Senior | Next Rank: 100 Posts; Posts: 53; Joined: Tue Feb 17, 2009 11:14 pm; Location: India; Thanked: 2 times

by electrico » Thu Jun 18, 2009 6:44 pm

I need help understanding the part 1. if x^2 > 1 then i know that x > 1 or x > -1 but how come x could be x < -1 ??

Here you are wrong deducting x>-1. when x > -1 => x = - 0.9, - 0.5, 4, 5, 100.....which is wrong.

the correct deduction is when x^2 > 1 => x> 1or x < - 1. and for the both case, x^2 > x. Hence A.

Thanks.

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