Find all School-related info fast with the new School-Specific MBA Forum

It is currently 27 Aug 2014, 11:34

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If ((ab)^2+3ab-18)((a-1)(a+2))=0 where a and b are integers

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
User avatar
Status: struggling with GMAT
Joined: 06 Dec 2012
Posts: 307
Location: Bangladesh
Concentration: Accounting
GMAT Date: 04-06-2013
GPA: 3.65
Followers: 8

Kudos [?]: 99 [0], given: 46

If ((ab)^2+3ab-18)((a-1)(a+2))=0 where a and b are integers [#permalink] New post 15 Dec 2012, 11:48
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

36% (02:00) correct 64% (01:36) wrong based on 67 sessions
If \frac{(ab)^2+3ab-18}{(a-1)(a+2)}= 0 where a and b are integers,which of the following could be the value of b?

I. 1
II. 2
III. 3

(A) I only
(B) II only
(C) I and II only
(D) I and III only
(E) I, II and III only
[Reveal] Spoiler: OA

Last edited by Bunuel on 16 Dec 2012, 06:20, edited 1 time in total.
Renamed the topic and edited the question.
1 KUDOS received
Intern
Intern
User avatar
Joined: 24 Apr 2012
Posts: 48
Followers: 0

Kudos [?]: 13 [1] , given: 1

Re: If \frac{(ab)^2+3ab-18}{(a-1)(a+2)}=0 [#permalink] New post 16 Dec 2012, 03:22
1
This post received
KUDOS
Ans:

from the fraction we get that “a” cannot be 1 or -2, so putting the value of a in numerator we get the the values of “b” to 3,-6, -3/2 , therefore b cannot be 3 so the answer is (C).
_________________

www.mnemoniceducation.com

TURN ON YOUR MINDS!!!

Intern
Intern
avatar
Joined: 15 Aug 2012
Posts: 11
Followers: 0

Kudos [?]: 3 [0], given: 13

Re: If ((ab)^2+3ab-18)((a-1)(a+2))=0 where a and b are integers [#permalink] New post 16 Dec 2012, 06:29
From the Q,

Numerator = 0 whereas Denominator <> (cannot be) 0

Numerator = 0 provides: ab = -6 or ab = 3
Denominator <> 0 provides: a <> 1 and a <> -2

Put values of b in to ab to check for a:

1) b = 1; a = -6 or a = 3
2) b = 2; a = -3 or a = 3/2
3) b = 3; a = -2 or a = 1

But a <> 1 and a <> -2,

Hence, b can not be 3 and could be either 1 or 2.
Ans: C
Manager
Manager
User avatar
Joined: 24 Mar 2010
Posts: 81
Followers: 0

Kudos [?]: 18 [0], given: 134

Re: If ((ab)^2+3ab-18)((a-1)(a+2))=0 where a and b are integers [#permalink] New post 20 Dec 2012, 12:50
mun23 wrote:
If \frac{(ab)^2+3ab-18}{(a-1)(a+2)}= 0 where a and b are integers,which of the following could be the value of b?

I. 1
II. 2
III. 3

(A) I only
(B) II only
(C) I and II only
(D) I and III only
(E) I, II and III only



For the \frac{(ab)^2+3ab-18}{(a-1)(a+2)}= 0 = 0

numerator has to be zero
and a # 1 and a # -2 (Since these two values would make denominator zero and fraction undefined)

Now (ab)^2+3ab-18

Put ab = x

x^2 + 3x - 18

factorized to

(x-3)(x+6)

Case I
x = ab = 3, => a =1 , b = 3 -- NOT POSSIBLE as we cannot have a = 1
x = ab = 3, => a =3 , b = 1 -- POSSIBLE

Case II
x = ab = -6, => a = -1, 2,+3,+6 & b = +2, -3, +6

Hence we can note that b can assume values 1 & 2 but not 3.

Hence C
_________________

- Stay Hungry, stay Foolish -

Expert Post
Veritas Prep GMAT Instructor
User avatar
Joined: 16 Oct 2010
Posts: 4687
Location: Pune, India
Followers: 1080

Kudos [?]: 4844 [0], given: 163

Re: If ((ab)^2+3ab-18)((a-1)(a+2))=0 where a and b are integers [#permalink] New post 20 Dec 2012, 20:25
Expert's post
mun23 wrote:
If \frac{(ab)^2+3ab-18}{(a-1)(a+2)}= 0 where a and b are integers,which of the following could be the value of b?

I. 1
II. 2
III. 3

(A) I only
(B) II only
(C) I and II only
(D) I and III only
(E) I, II and III only


For \frac{(ab)^2+3ab-18}{(a-1)(a+2)}= 0 to hold, (ab)^2+3ab-18 = 0

You need 'a' to be an integer so put in the values of b to check whether you get integral values for 'a'
b = 1 => a^2 + 3a - 18 = 0 => (a + 6)(a - 3) = 0 => Integral values so acceptable
b = 2 => 4a^2 + 6a - 18 = 0 => (2a + 6)(2a - 3) = 0 => We get a = -3 (an integer) hence acceptable
b = 3 => 9a^2 + 9a - 18 = 0 => (a + 2)(a - 1) = 0 => We get a = -2 or 1. a can take neither of these values since they make the denominator 0. Not acceptable

Answer (C)
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Save $100 on Veritas Prep GMAT Courses And Admissions Consulting
Enroll now. Pay later. Take advantage of Veritas Prep's flexible payment plan options.

Veritas Prep Reviews

Re: If ((ab)^2+3ab-18)((a-1)(a+2))=0 where a and b are integers   [#permalink] 20 Dec 2012, 20:25
    Similar topics Author Replies Last post
Similar
Topics:
3 Experts publish their posts in the topic If the three-digit integer x=”abc”, where a, b, and c BDSunDevil 3 04 May 2012, 06:21
1 Experts publish their posts in the topic If a b > a + b, where a and b are integers, which of the girishkakkar 12 30 Jan 2011, 21:18
Let a and b be integers where b<0 and a>b. If (a + tekno9000 2 15 Aug 2008, 07:30
a,b,c are consecutire integers where a < b < c. Which alimad 3 17 Sep 2007, 12:55
a, b and c are 3 digit integers, where a=b+c. Is the getzgetzu 7 26 Apr 2006, 02:55
Display posts from previous: Sort by

If ((ab)^2+3ab-18)((a-1)(a+2))=0 where a and b are integers

  Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group and phpBB SEO

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®.