In the equation x^2 + bx + 12 = 0, x is a variable and b is : GMAT Data Sufficiency (DS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 24 Jan 2017, 15:28

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# In the equation x^2 + bx + 12 = 0, x is a variable and b is

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 36638
Followers: 7106

Kudos [?]: 93661 [0], given: 10583

In the equation x^2 + bx + 12 = 0, x is a variable and b is [#permalink]

### Show Tags

29 Jan 2014, 01:14
Expert's post
5
This post was
BOOKMARKED
00:00

Difficulty:

5% (low)

Question Stats:

79% (01:53) correct 21% (00:55) wrong based on 379 sessions

### HideShow timer Statistics

The Official Guide For GMAT® Quantitative Review, 2ND Edition

In the equation x^2 + bx + 12 = 0, x is a variable and b is a constant. What is the value of b ?

(1) x - 3 is a factor of x^2 + bx + 12.
(2) 4 is a root of the equation x^2 + bx + 12 = 0.

Data Sufficiency
Question: 62
Category: Algebra First- and second-degree equations
Page: 157
Difficulty: 600

GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!
[Reveal] Spoiler: OA

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 36638
Followers: 7106

Kudos [?]: 93661 [1] , given: 10583

Re: In the equation x^2 + bx + 12 = 0, x is a variable and b is [#permalink]

### Show Tags

29 Jan 2014, 01:15
1
KUDOS
Expert's post
SOLUTION

In the equation x^2 + bx + 12 = 0, x is a variable and b is a constant. What is the value of b ?[b][/b]

(1) x-3 is a factor of x^2 + bx + 12 --> simply means that x=3 is a root of x^2+bx+12=0 (if x-3 is a factor of x^2+bx+12 then x^2+bx+12=(x-3)(x-k)=0, for some k, so x=3 is on of the roots of the equation) --> substitute x=3: 3^2+3b+12=0 --> b=-7. Sufficient.

(2) 4 is a root of x^2 + bx + 12 = 0 --> the same here, substitute x=4: 4^2+4b+12=0 --> b=-7. Sufficient.

_________________
Senior Manager
Joined: 20 Dec 2013
Posts: 273
Location: India
Followers: 0

Kudos [?]: 81 [0], given: 29

Re: In the equation x^2 + bx + 12 = 0, x is a variable and b is [#permalink]

### Show Tags

29 Jan 2014, 01:51
From S1:x-3 is a factor of the given equation=>x=3 is a root of the equation.Putting x=3 in the eq x^2+bx+12 we can get the value of b.Hence sufficient.
From S2:4 is a root of the equation=>Putting x=4 in the equation we can find out b.Sufficient.
Ans.D
Math Expert
Joined: 02 Sep 2009
Posts: 36638
Followers: 7106

Kudos [?]: 93661 [0], given: 10583

Re: In the equation x^2 + bx + 12 = 0, x is a variable and b is [#permalink]

### Show Tags

01 Feb 2014, 08:45
SOLUTION

In the equation x^2 + bx + 12 = 0, x is a variable and b is a constant. What is the value of b ?[b][/b]

(1) x-3 is a factor of x^2 + bx + 12 --> simply means that x=3 is a root of x^2+bx+12=0 (if x-3 is a factor of x^2+bx+12 then x^2+bx+12=(x-3)(x-k)=0, for some k, so x=3 is on of the roots of the equation) --> substitute x=3: 3^2+3b+12=0 --> b=-7. Sufficient.

(2) 4 is a root of x^2 + bx + 12 = 0 --> the same here, substitute x=4: 4^2+4b+12=0 --> b=-7. Sufficient.

_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13549
Followers: 578

Kudos [?]: 163 [0], given: 0

Re: In the equation x^2 + bx + 12 = 0, x is a variable and b is [#permalink]

### Show Tags

09 Sep 2016, 21:01
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.
_________________
Re: In the equation x^2 + bx + 12 = 0, x is a variable and b is   [#permalink] 09 Sep 2016, 21:01
Similar topics Replies Last post
Similar
Topics:
In the equation x^2 + 5x + k = 0, k is a constant and x is a variable. 1 11 Nov 2016, 00:17
2 In the equation x^2 + bx + 7= 0, where x is a variable, and b is a con 1 24 Aug 2016, 22:04
10 In the equation x^2+bx+c=0, b and c are constants, and x is 2 06 Mar 2014, 20:26
103 If r and s are the roots of the equation x^2 + bx + c = 0 35 20 Oct 2012, 11:12
11 In the equation x^2+bx+12=0, x is a variable and b is a 19 21 Feb 2011, 04:38
Display posts from previous: Sort by