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

It is currently 19 Jul 2018, 10:46

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

What is the value of | (x+5)/(x+7) |? (1) x2 + 7x – 18 = 0 (2) 3x2 + 4

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

Hide Tags

Top Contributor
Senior RC Moderator
User avatar
P
Status: It always seems impossible until it's done!!
Joined: 29 Aug 2012
Posts: 1178
Location: India
WE: General Management (Aerospace and Defense)
GMAT ToolKit User Premium Member Reviews Badge CAT Tests
What is the value of | (x+5)/(x+7) |? (1) x2 + 7x – 18 = 0 (2) 3x2 + 4  [#permalink]

Show Tags

New post 04 Aug 2017, 09:24
Top Contributor
5
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

32% (01:31) correct 68% (02:09) wrong based on 186 sessions

HideShow timer Statistics

What is the value of | \(\frac{(x+5)}{(x+7)}\) |?

(1) \(x^2 + 7x – 18 = 0\)

(2) \(3x^2 + 46x + 171 = 0\)

_________________

Become a GMAT Club Premium member to avail lot of discounts

Most Helpful Expert Reply
Expert Post
3 KUDOS received
GMAT Tutor
avatar
S
Joined: 24 Jun 2008
Posts: 1345
Re: What is the value of | (x+5)/(x+7) |? (1) x2 + 7x – 18 = 0 (2) 3x2 + 4  [#permalink]

Show Tags

New post 04 Aug 2017, 10:30
3
2
Each statement will give us two solutions for x. We can then plug these two values of x in to the expression in the question, and if we get the same answer both times, the statement is sufficient, and if we get two different answers, the statement is not sufficient.

x^2 + 7x - 18 = 0
(x + 9)(x - 2) = 0
x = -9 or x = 2

If you plug these two values of x in to the question, you get two different answers, so Statement 1 is not sufficient.

Looking at Statement 2:

3x^2 + 46x + 171 = 0
(3x + something)(x + something else) = 0

Here the two "something" numbers must multiply to 171. Ordinarily we'd need to work out the divisors of 171, and possibly try out a few divisors until we found the pair that "works" (i.e. that gives "+46x" as the middle term if you multiply the two factors back together), which takes a long time and is the reason you never need to do this kind of factoring on the real GMAT. But we know the two Statements in a GMAT DS question must be consistent. There must be at least one value of x that works in both statements. Since x+9 and x-2 were the only factors in Statement 1, and since we want a factor that includes a number which is a divisor of 171, it must be that x+9 is a factor of the quadratic in Statement 2. So our factorization is

3x^2 + 46x + 171 = (3x + 19) (x + 9)

and just to be sure, we can multiply the right side back out to confirm this is correct. If we do that, we do get "46x" in the middle, so this is the correct factorization. So the two solutions for x are x = -9 and x = -19/3, and if you plug those back in to the question, you get an answer of 2 either way, so Statement 2 is sufficient alone.
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

General Discussion
Manager
Manager
avatar
G
Joined: 27 Jan 2016
Posts: 145
Schools: ISB '18
GMAT 1: 700 Q50 V34
Re: What is the value of | (x+5)/(x+7) |? (1) x2 + 7x – 18 = 0 (2) 3x2 + 4  [#permalink]

Show Tags

New post 04 Aug 2017, 09:42
Stmnt 1) x=-9,2

Substituting these two values in the given expression gives us two different values

Stmnt 2) x=-9,-19/3

Both these values result in the one solution i.e 2, when substitued in the given expression. Hence suff
SVP
SVP
avatar
P
Joined: 12 Dec 2016
Posts: 1869
Location: United States
GMAT 1: 700 Q49 V33
GPA: 3.64
GMAT ToolKit User Premium Member
Re: What is the value of | (x+5)/(x+7) |? (1) x2 + 7x – 18 = 0 (2) 3x2 + 4  [#permalink]

Show Tags

New post 22 Aug 2017, 01:21
so, there is no way to test whether both values of x in st2 will cause the ABS to have the same value?
Intern
Intern
avatar
B
Joined: 18 Aug 2017
Posts: 30
GMAT 1: 670 Q49 V33
Re: What is the value of | (x+5)/(x+7) |? (1) x2 + 7x – 18 = 0 (2) 3x2 + 4  [#permalink]

Show Tags

New post 25 Aug 2017, 01:55
It took me almost 4 mins to solve for all the value of x and to plug them back in for testing.
Is there any faster way to do 700+ level algebra DS like this one? Is it worth to spend that much time on such a question, if you know you can get it right but you have to spend twice as much time as you are allowed?
Re: What is the value of | (x+5)/(x+7) |? (1) x2 + 7x – 18 = 0 (2) 3x2 + 4 &nbs [#permalink] 25 Aug 2017, 01:55
Display posts from previous: Sort by

What is the value of | (x+5)/(x+7) |? (1) x2 + 7x – 18 = 0 (2) 3x2 + 4

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

Events & Promotions

PREV
NEXT


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®.