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

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0559 reviews
Vote for Target Test Prep, Newsweek Readers’ Choice Awards 2026
NEWSWEEK READERS’ CHOICE 2026

BIG NEWS! Target Test Prep has been nominated, and they’d love your vote!

TTP has worked incredibly hard to build the best test prep experience possible, and winning Newsweek’s 2026 Readers’ Choice Award for Best Test Prep would mean a lot to them. If TTP has helped you, they’d be incredibly grateful for your vote. You can vote once each day through September 9.

Vote for TTP
GMATLiveTeach 7 seats left
Chris Peckover
NEXT LIVE COHORT

Oct 13 to Jan 7, 2027

with Chris Peckover

Schedule
Tue, Thu · 8:00 to 10:00 PM ET
Included
40 live hours + 6 months of GMAT OnDemand
  • Live instruction and real-time questions
  • Class recordings and assigned practice
View class & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll
Limited cohort · enrollment openTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

What is the value of x?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Sat Jan 30, 2010 3:24 pmFollowed by: 2 members
Location: San Francisco, CA
Thanked: 1 times
by suzeemunkee » Thu Jul 29, 2010 7:37 am
What is the value of x?

(1) sqrt(x^4) = 9
(2) sqrt(x^2) = -x

The issue I can't figure out with this problem is: Why can't we assume that Statement 1 will always yield a positive number? Here's my logic: Since sqrt(x^2) equals the absolute value of x, why can't we assume that sqrt(x^4), which is the same as sqrt(x^2*x^2), will also always be positive?

The OA is C. The question is from beat the gmat's SmartGMAT (which I love!) practice.

Thanks guys for any help you can provide :)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |
User avatar
Legendary Member
Posts: 1460
Joined: Tue Dec 29, 2009 1:28 amFollowed by: 7 members
Thanked: 135 times

by selango » Thu Jul 29, 2010 7:56 am
stmt1,

sqrt(x^4) = 9

x can be sqrt(3) or -sqrt(3)

Insuff

stmt2,

sqrt(x^2) = -x

No info abt X or sqrt(x^2)

Insuff

Combining 1 and 2,

sqrt(x^4) = 9

x^2=9

sqrt(x^2)=3

x=sqrt(3) or x=-sqrt(3)

we know that sqrt(x^2) = -x

-->x=-sqrt(3)

Pick C
--Anand--
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 1460
Joined: Tue Dec 29, 2009 1:28 amFollowed by: 7 members
Thanked: 135 times

by selango » Thu Jul 29, 2010 8:06 am
The issue I can't figure out with this problem is: Why can't we assume that Statement 1 will always yield a positive number? Here's my logic: Since sqrt(x^2) equals the absolute value of x, why can't we assume that sqrt(x^4), which is the same as sqrt(x^2*x^2), will also always be positive?
sqrt(x^4) = 9

sqrt(x^2*x^2)=9

x^2 is positive.However x can be positive or negative.

For ex sqrt(x^4)=4

sqrt(x^2*x^2)=4

x^2 is 4.Here x^2 is positive.

However x^2=4.x can be 2 or -2

Hence we cant determine value of x.

Hope this clarify
--Anand--
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Sat Jan 30, 2010 3:24 pmFollowed by: 2 members
Location: San Francisco, CA
Thanked: 1 times

by suzeemunkee » Thu Jul 29, 2010 8:23 am
selango wrote:
The issue I can't figure out with this problem is: Why can't we assume that Statement 1 will always yield a positive number? Here's my logic: Since sqrt(x^2) equals the absolute value of x, why can't we assume that sqrt(x^4), which is the same as sqrt(x^2*x^2), will also always be positive?
sqrt(x^4) = 9

sqrt(x^2*x^2)=9

x^2 is positive.However x can be positive or negative.

For ex sqrt(x^4)=4

sqrt(x^2*x^2)=4

x^2 is 4.Here x^2 is positive.

However x^2=4.x can be 2 or -2

Hence we cant determine value of x.

Hope this clarify

A beam of light was just shed upon my noggin :) Thank you selango.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1