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

It is currently 09 Dec 2018, 20:19

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
  • Free GMAT Algebra Webinar

     December 09, 2018

     December 09, 2018

     07:00 AM PST

     09:00 AM PST

    Attend this Free Algebra Webinar and learn how to master Inequalities and Absolute Value problems on GMAT.
  • Free lesson on number properties

     December 10, 2018

     December 10, 2018

     10:00 PM PST

     11:00 PM PST

    Practice the one most important Quant section - Integer properties, and rapidly improve your skills.

If f(x) = x^3 + 9, is f(x) positive?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51035
If f(x) = x^3 + 9, is f(x) positive?  [#permalink]

Show Tags

New post 08 Feb 2017, 00:46
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

58% (01:30) correct 42% (00:52) wrong based on 160 sessions

HideShow timer Statistics

Senior Manager
Senior Manager
User avatar
G
Joined: 19 Apr 2016
Posts: 274
Location: India
GMAT 1: 570 Q48 V22
GMAT 2: 640 Q49 V28
GPA: 3.5
WE: Web Development (Computer Software)
If f(x) = x^3 + 9, is f(x) positive?  [#permalink]

Show Tags

New post 08 Feb 2017, 01:47
1
1
Bunuel wrote:
If f(x) = x^3 + 9, is f(x) positive?

(1) x < −1

(2) x > −3


St I
x < -1
if x = -2 we have \((-2)^3+9\) = 1 f(x) is positive.
if x = -3 we have \((-3)^3+9\) = -18 f(x) is negative ----------Insufficient.

St II
x > -3
if x = -2 we have \((-2)^3+9\) = 1 f(x) is positive.
if x = -2.5 we have \((-2.5)^3+9\) = -6.25 f(x) is negative. ----------Insufficient.

St. I and II ----------Insufficient.

Hence Option E is correct.
Hit Kudos if you liked it 8-)
Manager
Manager
avatar
S
Joined: 13 Dec 2013
Posts: 156
Location: United States (NY)
Concentration: General Management, International Business
GMAT 1: 710 Q46 V41
GMAT 2: 720 Q48 V40
GPA: 4
WE: Consulting (Consulting)
Reviews Badge
Re: If f(x) = x^3 + 9, is f(x) positive?  [#permalink]

Show Tags

New post 08 Feb 2017, 10:10
Bunuel wrote:
If f(x) = x^3 + 9, is f(x) positive?

(1) x < −1

(2) x > −3


1) If x is -2 f(x) is +ve. If x is -3 f(x) is -ve. Not suff.
2) If x is -2 f(x) is +ve. If x is -2.9 f(x) is -ve. Not suff.
1)&2) Constraints for 2) still apply. Not suff. E.
Senior SC Moderator
User avatar
V
Joined: 14 Nov 2016
Posts: 1323
Location: Malaysia
GMAT ToolKit User Premium Member CAT Tests
If f(x) = x^3 + 9, is f(x) positive?  [#permalink]

Show Tags

New post 11 Feb 2017, 20:06
Bunuel wrote:
If \(f(x) = x^3 + 9\), is \(f(x)\) positive?

(1) \(x < −1\)

(2) \(x > −3\)


Official solution from Veritas Prep.

If \(x<−1\), then x could be \(−2\) in which case \(f(x)\) is positive or \(x\) could be \(−3\) in which case \(f(x)\) is negative. Therefore, Statement 1 alone is not sufficient.

If \(x>−3\), the x could be \(−2\) in which case \(f(x)\) is positive. However, the problem never stated that \(x\) is an integer. Then, \(x\) could be \(-2.99999\), that is almost \(-3\). In this case, \(f(x)\) will be a negative. \(f(x)=(-2.99999)^3+9 = -17.99973\) Therefore, Statement 2 is not sufficient.

Combining Statement 1 and Statement 2, \(f(x)\) could still either be positive or negative. Therefore, the answer is \(E\).
_________________

"Be challenged at EVERY MOMENT."

“Strength doesn’t come from what you can do. It comes from overcoming the things you once thought you couldn’t.”

"Each stage of the journey is crucial to attaining new heights of knowledge."

Rules for posting in verbal forum | Please DO NOT post short answer in your post!

Advanced Search : https://gmatclub.com/forum/advanced-search/

Manager
Manager
avatar
S
Joined: 24 Oct 2013
Posts: 137
Location: India
Concentration: General Management, Strategy
WE: Information Technology (Computer Software)
Re: If f(x) = x^3 + 9, is f(x) positive?  [#permalink]

Show Tags

New post 13 Feb 2017, 00:48
I think it should be B.

(-2.9999)^3 is less than 9 and therefor -899999+9 >0

Hence it should be B
Senior Manager
Senior Manager
User avatar
G
Joined: 19 Apr 2016
Posts: 274
Location: India
GMAT 1: 570 Q48 V22
GMAT 2: 640 Q49 V28
GPA: 3.5
WE: Web Development (Computer Software)
Re: If f(x) = x^3 + 9, is f(x) positive?  [#permalink]

Show Tags

New post 13 Feb 2017, 01:28
deepthit wrote:
I think it should be B.

(-2.9999)^3 is less than 9 and therefor -899999+9 >0

Hence it should be B


(-2.9999)^3 = -26.997300 < 0. :)
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 9082
Premium Member
Re: If f(x) = x^3 + 9, is f(x) positive?  [#permalink]

Show Tags

New post 04 Apr 2018, 22:08
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.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

GMAT Club Bot
Re: If f(x) = x^3 + 9, is f(x) positive? &nbs [#permalink] 04 Apr 2018, 22:08
Display posts from previous: Sort by

If f(x) = x^3 + 9, is f(x) positive?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

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®.