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 →

functions f(a + b) = f(a) + f(b) for all positive numbers...

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 28
Joined: Sat May 26, 2007 10:12 am
Thanked: 1 times
by galinaphillips » Sat Jun 02, 2007 4:44 am
My question is how to solve this problem from the MBA.com software test 1:

For which of the following functions is f(a + b) = f(a) + f(b) for all positive numbers a and b?

Possible answers are:

f(x) = x^2

f(x) = x + 1

f(x) = sqrt x

f(x) = 2/x

f(x) = -3x

The correct answer is f(x) = -3x but I'm not sure how to solve.

Thanks!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 105
Joined: Mon Sep 18, 2006 12:34 pm
Location: OH
Thanked: 7 times
GMAT Score:780

by mschling52 » Sat Jun 02, 2007 12:02 pm
The approach I would take is to plug in a+b in place of x into each function (this is f(a+b)) then see if you can rearrange to get something equal to f(a)+f(b).

A. f(a+b) = (a+b)^2 = a^2 + 2ab + b^2 = f(a)+f(b)+2ab
B. f(a+b) = a + b + 1 = f(b) + a
C. f(a+b) = sqrt(a+b) not equal f(a)+f(b) = sqrt(a)+sqrt(b)
D. f(a+b) = 2/(a+b) not equal f(a)+f(b) = 2/a + 2/b
E. 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: 28
Joined: Sat May 26, 2007 10:12 am
Thanked: 1 times

functions f(a + b) = f(a) + f(b) for all positive numbers...

by galinaphillips » Sat Jun 02, 2007 4:33 pm
Thanks a lot! It was very helpful. :)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1