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 →

Function Test OG

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Community Manager
Posts: 363
Joined: Sun Dec 10, 2006 12:24 pmFollowed by: 3 members
Location: St. Louis
Thanked: 7 times
by isisalaska » Sun Jan 07, 2007 4:41 pm
For which of the following functions is f(a+b) = f(a) + f(b) for all positive numbers a and b

f(x)=x^2
f(x)=x+1
f(x)=Sq.root x
f9x)=2/x
f9x)=-3x

Why is -3x?

thanks!
Isis Alaska
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Senior | Next Rank: 100 Posts
Posts: 41
Joined: Fri Dec 15, 2006 9:23 amFollowed by: 1 member
Location: Greece

by thankont » Mon Jan 08, 2007 12:10 am
f(a)=-3a, f(b) = -3b, f(a+b) = -3(a+b) = (-3a)+(-3b) = f(a)+f(b)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 19
Joined: Thu Dec 07, 2006 3:20 am

by Chrystelle » Fri Jan 12, 2007 5:02 am
Hi guys

I am confused here

f(a)+f(b) = sqrt(a)+sqrt(b) =sqrt(a+b)=f(a+b)

f(a)+f(b) = -3a-3b =-3(a+b) = f(a+b)

That leaves with 2 answers sqrt(x) and -3x
So, which one do we have to choose?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 2469
Joined: Thu Apr 20, 2006 12:09 pmFollowed by: 14 members
Location: BtG Underground
Thanked: 85 times

by aim-wsc » Fri Jan 12, 2007 6:41 am
Chrystelle wrote:Hi guys

I am confused here

f(a)+f(b) = sqrt(a)+sqrt(b) =sqrt(a+b)=f(a+b)

?

INCORRECT.

sqrt 3 + sqrt 2 IS NOT sqrt 5.

I HOPE YOU GOT MY POINT. :)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Senior | Next Rank: 100 Posts
Posts: 41
Joined: Fri Dec 15, 2006 9:23 amFollowed by: 1 member
Location: Greece

by thankont » Fri Jan 12, 2007 6:44 am
be careful here:
sqrt(4) = 2
sqrt(9) = 3
sqrt(4) + sqrt(9) = 5
but sqrt(4+9) = sqrt(13) <>5
put some values to check
thanx
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 22
Joined: Fri May 04, 2007 3:51 am

by krishnamurthyu » Sat Aug 18, 2007 7:13 pm
f(a) + f(b) f(a+b)
f(x)=x^2 ==> a^2 + b^2 != (a+b)^2
f(x)=x+1 ==> a+1 + b+1 != (a+b)+1
f(x)=Sq.root x ==> Rt(a) + Rt (b) != Rt(a+b)
f(x)=2/x ==> 2/a + 2/b != 2/(a+b)
f(x)=-3x ==> -3a + (-3b) = -3(a+b)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1