It is currently 17 Nov 2017, 10:41

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Is x > 0? 1) x^3+x^2+x<0 2) x^2<1

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

Hide Tags

Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 4313

Kudos [?]: 3032 [0], given: 0

GPA: 3.82
Is x > 0? 1) x^3+x^2+x<0 2) x^2<1 [#permalink]

Show Tags

06 Nov 2017, 21:51
Expert's post
1
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

84% (00:40) correct 16% (01:35) wrong based on 37 sessions

HideShow timer Statistics

[GMAT math practice question]

Is $$x > 0$$?

1) $$x^3+x^2+x<0$$
2) $$x^2<1$$
[Reveal] Spoiler: OA

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Kudos [?]: 3032 [0], given: 0

Intern
Joined: 28 Dec 2010
Posts: 48

Kudos [?]: 13 [0], given: 7

Re: Is x > 0? 1) x^3+x^2+x<0 2) x^2<1 [#permalink]

Show Tags

06 Nov 2017, 21:56
1. $$x^3 + x^2 + x > 0$$
$$x ( x^2 + x + 1) > 0$$

Here $$x^2 + x + 1 is always > 0$$
So x<0
Sufficient.

2. $$x^2<1$$
$$(x+1)(x-1) < 0$$
x>-1 ; x < 1
Insufficient.

A.
_________________

_________________________________________
Please Kudos, if you found this post helpful.

Kudos [?]: 13 [0], given: 7

Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 4313

Kudos [?]: 3032 [0], given: 0

GPA: 3.82
Re: Is x > 0? 1) x^3+x^2+x<0 2) x^2<1 [#permalink]

Show Tags

09 Nov 2017, 00:42
=>

Forget conventional ways of solving math questions. In DS, VA (Variable Approach) method is the easiest and quickest way to find the answer without actually solving the problem. Remember that equal number of variables and independent equations ensures a solution.

Since we have 1 variable and 0 equation, D is most likely to be the answer.

Conditions 1) x^3+x^2+x<0
x(x^2+x+1)<0 implies x < 0, since x^2+x+1 > 0.
The answer is no.
Since “no” is also an answer according to CMT (Common Mistake Time) 1, this is sufficient.

Condition 2) x^2<1
We have x2-1 < 0 and (x+1)(x-1) < 0.
Thus, you get -1 < x < 1 according to the “between” rule in inequalities.
This is not sufficient.

Therefore, A is the answer.

For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both con 1) and con 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. D is most likely to be the answer using con 1) and con 2) separately according to DS definition. Obviously, there may be cases where the answer is A, B, C or E.
Ans: A
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Kudos [?]: 3032 [0], given: 0

Re: Is x > 0? 1) x^3+x^2+x<0 2) x^2<1   [#permalink] 09 Nov 2017, 00:42
Display posts from previous: Sort by

Is x > 0? 1) x^3+x^2+x<0 2) x^2<1

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

 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®.