Function question

Expert replies

anthony.j: Junior | Next Rank: 30 Posts; Posts: 26; Joined: Mon Apr 27, 2009 6:37 am; Location: South NJ, right outside of Philly; Thanked: 1 times; GMAT Score:420

by anthony.j » Sun May 03, 2009 12:46 pm

How would you go about solving this question?

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

a - f(x) = x^2
b - f(x) = x+1
c - f(x) = sqrt of x
d - f(x) = 2/x
e - f(x) = -3x

answer is f(x) = -3x

Thanks!

Like this post

Source: Beat The GMAT — Problem Solving | Sun May 03, 2009 12:46 pm

artistocrat: Master | Next Rank: 500 Posts; Posts: 152; Joined: Wed Mar 12, 2008 4:36 pmFollowed by: 2 members; Thanked: 8 times

by artistocrat » Sun May 03, 2009 1:38 pm

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

f(x)=-3x

lets use, a=2 & b=3:

then f(a)=-3(2)=-6
and f(b)=-3(3)=-9

and f(a+b)=f(5)=-15

so definitely f(a+b)=f(a)+f(b)

I hope it helps

Like this post

lilu: Master | Next Rank: 500 Posts; Posts: 148; Joined: Wed Dec 10, 2008 5:13 pm; Location: SF, CA; Thanked: 12 times

by lilu » Sun May 03, 2009 4:41 pm

https://www.beatthegmat.com/f-a-b-f-a-f-b-t35045.html

DanaJ gives an excellent explanation to this problem in the link attached

The more you look, the more you see.

Like this post

anthony.j: Junior | Next Rank: 30 Posts; Posts: 26; Joined: Mon Apr 27, 2009 6:37 am; Location: South NJ, right outside of Philly; Thanked: 1 times; GMAT Score:420

by anthony.j » Sun May 03, 2009 5:12 pm

Awesome! Thank you for the link.

Next time I will try typing the problem in as my search term. Never thought of that. Double thanks!

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review