GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 26 Sep 2018, 03:57

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Is x negative? 1) x^3(1-x^2) < 0 2) x^2 - 1 < 0

Author Message
Director
Joined: 23 May 2008
Posts: 730
Is x negative? 1) x^3(1-x^2) < 0 2) x^2 - 1 < 0  [#permalink]

### Show Tags

08 Jun 2009, 23:24
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (01:37) wrong based on 3 sessions

### HideShow timer Statistics

Is x negative?

1) x^3(1-x^2) < 0
2) x^2 - 1 < 0

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Director
Joined: 03 Jun 2009
Posts: 751
Location: New Delhi
WE 1: 5.5 yrs in IT
Re: OG 11 DS #154  [#permalink]

### Show Tags

09 Jun 2009, 00:03
1) x^3(1-x^2) < 0: Insufficient
Let x is -ve
=> x^3 < 0 and 1-x^2 >0

for 1-x^2 >0
only possible when -1<x<1, but we don't have any info on this.

2) x^2 - 1 < 0: Insufficient
possible when -1<x<1
so, x can be both +ve or -ve

Together: Sufficient
_________________
Manager
Joined: 14 May 2009
Posts: 187
Re: OG 11 DS #154  [#permalink]

### Show Tags

09 Jun 2009, 00:53
1
bigtreezl wrote:
Is x negative?

1) x^3(1-x^2) < 0
2) x^2 - 1 < 0

Question:$$(x<0?)$$

(1) $$x^{3}(1-x^{2})<0$$
==> $$x^3<0$$ & $$1-x^{2}>0$$
==> $$x<0$$ & $$(x^{2}<1 ==> -1<x<1)$$
==> $$-1<x<0$$ ==> YES

or
==> $$x^3>0$$ & $$1-x^{2}<0$$
==> $$x>0$$ & $$x^{2}>1$$
==> $$x>0$$ & $$(x<-1 or x>1)$$
==> $$x>1$$ ==> NO

YES&NO==> INSUFFICIENT

(2) $$x^2 - 1<0$$
==> $$x^2<1$$ ==> $$-1<x<1$$ ==> YES/NO, INSUFFICIENT

(1&2) Rearrange $$x^2 - 1<0$$
to $$-(1-x^2)<0$$
then to $$1-x^2>0$$

So $$1-x^2$$ is +
sub into equation 1
(1) $$x^{3}+<0$$
$$x^3<0$$
==> x<0

SUFFICIENT

Final Answer, $$C$$.
_________________

Non-Human User
Joined: 09 Sep 2013
Posts: 8195
Re: Is x negative? 1) x^3(1-x^2) < 0 2) x^2 - 1 < 0  [#permalink]

### Show Tags

15 Nov 2017, 07:02
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

_________________
Re: Is x negative? 1) x^3(1-x^2) < 0 2) x^2 - 1 < 0 &nbs [#permalink] 15 Nov 2017, 07:02
Display posts from previous: Sort by

# Is x negative? 1) x^3(1-x^2) < 0 2) x^2 - 1 < 0

## Events & Promotions

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.