• 1 Hour Free
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

• Free Practice Test & Review
How would you score if you took the GMAT

Available with Beat the GMAT members only code

• Free Veritas GMAT Class
Experience Lesson 1 Live Free

Available with Beat the GMAT members only code

• 5 Day FREE Trial
Study Smarter, Not Harder

Available with Beat the GMAT members only code

• Free Trial & Practice Exam
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Award-winning private GMAT tutoring
Register now and save up to $200 Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code ## If 1/x - 1/(x+1) (OG16) tagged by: Brent@GMATPrepNow This topic has 2 expert replies and 1 member reply boomgoesthegmat Senior | Next Rank: 100 Posts Joined 25 Apr 2016 Posted: 93 messages Thanked: 1 times #### If 1/x - 1/(x+1) (OG16) Thu May 19, 2016 3:49 pm Elapsed Time: 00:00 • Lap #[LAPCOUNT] ([LAPTIME]) If 1/x - 1/(x+1) = 1/(x+4), then x could be A) 0 B) -1 C) -2 D) -3 E) -4 OA: C Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums! ### GMAT/MBA Expert Rich.C@EMPOWERgmat.com Elite Legendary Member Joined 23 Jun 2013 Posted: 8703 messages Followed by: 460 members Thanked: 2732 times GMAT Score: 800 Thu May 19, 2016 5:05 pm Hi boomgoesthegmat, I'm going to give you some hints so that you can try this question on your own: The GMAT does NOT test you on the concept of 'undefined' numbers, so you won't have to deal with a calculation that is divided by 0. In this prompt, you'll notice that there are 3 fractions, but since none of them can be "over 0", we can eliminate the answers that would cause that to happen: 0, -1 and -4. That means there are only two possibilities: -2 or -3. By plugging those values into the equation, you should quickly be able to determine which one 'balances' out the equation. THAT answer will be your solution.... Final Answer: C GMAT assassins aren't born, they're made, Rich _________________ Contact Rich at Rich.C@empowergmat.com OptimusPrep Master | Next Rank: 500 Posts Joined 13 Mar 2015 Posted: 410 messages Followed by: 7 members Thanked: 120 times GMAT Score: 770 Thu May 19, 2016 8:02 pm boomgoesthegmat wrote: If 1/x - 1/(x+1) = 1/(x+4), then x could be A) 0 B) -1 C) -2 D) -3 E) -4 OA: C 1/x - 1/(x+1) = 1/(x+4) You can do this question both by testing values and algebraically. I will solve it algebraically x + 1 - x / (x)(x + 1) = 1/(x + 4) 1/x*(x + 1) = 1/(x + 4) x + 4 = x^2 + x x^2 = 4 x = 2 or -2 Correct Option: C _________________ Ankur 99th Percentile GMAT Tutor | Optimus Prep™ Optimus Prep™ GMAT Courses: www.Optimus-Prep.com/GMAT Free Online Trial Hour: http://www.optimus-prep.com/request-free-online-trial-hour/ Free GMAT Study Plan: http://www.optimus-prep.com/ebook/ Optimus Prep™ Rates: GMAT Private Tutoring Online:$80-100/hr.*
GMAT Private Tutoring In-Person: $130-150/hr.* GMAT On Demand Course:$299 (Use Discount Code BEATTHEGMAT111)*

*All GMAT Courses Have A 50 Points Score Improvement Or Full Refund Guarantee

### GMAT/MBA Expert

Brent@GMATPrepNow GMAT Instructor
Joined
08 Dec 2008
Posted:
10763 messages
Followed by:
1212 members
Thanked:
5144 times
GMAT Score:
770
Wed Aug 23, 2017 5:05 pm
boomgoesthegmat wrote:
If 1/x - 1/(x+1) = 1/(x+4), then x could be

A) 0
B) -1
C) -2
D) -3
E) -4

OA: C
Plugging in the answer choices is definitely faster, but here's an algebraic solution...

One way to eliminate fractions is to multiply both sides by the least common multiple (LCM) of all the denominators.
The LCM of x, x+1 and x+4 is (x)(x+1)(x+4)

Given: 1/x - 1/(x+1) = 1/(x+4)
Multiply both sides by (x)(x+1)(x+4) to get: (x)(x+1)(x+4)[1/x - 1/(x+1)] = (x)(x+1)(x+4)[1/(x+4)]
Simplify: (x+1)(x+4) - (x)(x+4) = (x)(x+1)
Expand: [x² + 5x + 4] - [x² + 4x] = x² + x
Simplify: x + 4 = x² + x
Rearrange: x² = 4
Solve: x = 2 OR x = -2

Cheers,
Brent

_________________
Brent Hanneson – Founder of GMATPrepNow.com
Use our video course along with

Check out the online reviews of our course
Come see all of our free resources

GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!

### Best Conversation Starters

1 Vincen 180 topics
2 lheiannie07 65 topics
3 Roland2rule 49 topics
4 ardz24 40 topics
5 LUANDATO 16 topics
See More Top Beat The GMAT Members...

### Most Active Experts

1 Brent@GMATPrepNow

GMAT Prep Now Teacher

146 posts
2 Rich.C@EMPOWERgma...

EMPOWERgmat

103 posts
3 GMATGuruNY

The Princeton Review Teacher

100 posts
4 EconomistGMATTutor

The Economist GMAT Tutor

92 posts
5 Jay@ManhattanReview

Manhattan Review

79 posts
See More Top Beat The GMAT Experts