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

It is currently 20 Nov 2018, 20:37

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 November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
  • All GMAT Club Tests are Free and open on November 22nd in celebration of Thanksgiving Day!

     November 22, 2018

     November 22, 2018

     10:00 PM PST

     11:00 PM PST

    Mark your calendars - All GMAT Club Tests are free and open November 22nd to celebrate Thanksgiving Day! Access will be available from 0:01 AM to 11:59 PM, Pacific Time (USA)
  • Free lesson on number properties

     November 23, 2018

     November 23, 2018

     10:00 PM PST

     11:00 PM PST

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

In the x-y plane y=p(x)=ax^2+bx+c pass through (-1,0) and

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

Hide Tags

Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6531
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
In the x-y plane y=p(x)=ax^2+bx+c pass through (-1,0) and  [#permalink]

Show Tags

New post 13 Nov 2017, 00:11
00:00
A
B
C
D
E

Difficulty:

  75% (hard)

Question Stats:

48% (01:47) correct 52% (02:45) wrong based on 48 sessions

HideShow timer Statistics

[GMAT math practice question]

In the x-y plane \(y=p(x)=ax^2+bx+c\) pass through (-1,0) and (1,0). Is \(p(0)<0\)?

1) \(a>0\)
2) \(b^2-4ac>0\)

_________________

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.
"Only $99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Intern
Intern
avatar
B
Joined: 28 Dec 2010
Posts: 49
Re: In the x-y plane y=p(x)=ax^2+bx+c pass through (-1,0) and  [#permalink]

Show Tags

New post 13 Nov 2017, 02:44
This is a parabola. Since it already has 2 roots, we need to find whether it is facing upwards or downwards.

1. It is facing upwards.
p(0) <0
Sufficient.

2. We already know this since it has 2 roots. It would be helpful to know if we didn't new those 2 points.
No additional info.
Insufficient.

A.
_________________

_________________________________________
Please Kudos, if you found this post helpful.

Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6531
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Re: In the x-y plane y=p(x)=ax^2+bx+c pass through (-1,0) and  [#permalink]

Show Tags

New post 15 Nov 2017, 00:49
=>

Forget conventional ways of solving math questions. In DS, Variable approach 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

p(-1) = a – b + c = 0
p(1) = a + b + c = 0
Since we have 3 variables, a, b and c and 2 equations, D is most like to be the answer.

Condition 1)

Attachment:
11.13.png
11.13.png [ 7.33 KiB | Viewed 397 times ]



Since the leading coefficient a is positive, the parabola is concave up and p(0) < 0.
This is sufficient.

Condition 2)
It means the graph intersects x-axis twice and that the discriminant is positive.
We have two cases that the parabola could be concave up or concave down.

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.

Answer: 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.
"Only $99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

GMAT Club Bot
Re: In the x-y plane y=p(x)=ax^2+bx+c pass through (-1,0) and &nbs [#permalink] 15 Nov 2017, 00:49
Display posts from previous: Sort by

In the x-y plane y=p(x)=ax^2+bx+c pass through (-1,0) and

  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®.