BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Roots problem 2

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 57
Joined: Mon Dec 21, 2009 6:27 am
Location: Melbourne, Australia
Thanked: 17 times

by [email protected] » Wed Mar 07, 2012 7:14 pm
Root(3-x)=1-root(2x)
3-x=(1-root(2x))^2
3-x=2x+1-2*root(2x)
3x=2*root(2x)+2 ---Eq 1

So 9x^2=(2*root(2x)+2)^2
=(4+8*root(2x)+8x)
=4(1+2x+2*root(2x))
=4(1+2x+3x-2) --substituting from Eq 1
=4(5x-1)
=20x-4

OA is E
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 18
Joined: Thu Nov 17, 2011 1:07 pm

by kjallow » Thu Mar 08, 2012 4:22 pm
someone please tell me this is a 700-800 level question! how is this to be done in less than 2 mins??

Good explanation though..i was able to work it to this point: 4(1+2x+2*root(2x)) but didn't think to re-substitute from eqn 1. Thanks a bunch!
[email protected] wrote:Root(3-x)=1-root(2x)
3-x=(1-root(2x))^2
3-x=2x+1-2*root(2x)
3x=2*root(2x)+2 ---Eq 1

So 9x^2=(2*root(2x)+2)^2
=(4+8*root(2x)+8x)
=4(1+2x+2*root(2x))
=4(1+2x+3x-2) --substituting from Eq 1
=4(5x-1)
=20x-4

OA is E
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 136
Joined: Wed Apr 08, 2009 12:09 pmFollowed by: 1 member
Thanked: 4 times

by Troika » Thu Mar 08, 2012 5:14 pm
Thank you for the very helpful solution!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 581
Joined: Sun Apr 03, 2011 7:53 amFollowed by: 5 members
Thanked: 52 times

by killer1387 » Thu Mar 08, 2012 6:43 pm
HG10 wrote:If root (3 - x) = 1 - root (2x), then 9x^2 =

(A) 5

(B) 8

(C) 2 - 3x

(D) 12 - 4x

(E) 20x - 4

OA: E
i proceeded as following (took me around 15 sec):
root (3 - x) = 1 - root (2x),(square both sides)
=>3-x = 1+ 2x- 2 root(2x),
=> 2 root(2x)= 3x-2, (square both sides)
=> 8x = 9x^2+ 4- 12x,
=> 9x^2=20x-4

hence E.

HTH.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1