pleas help....function question

Expert replies

bushra: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Tue Dec 04, 2007 10:32 am; Location: canada

by bushra » Thu Dec 06, 2007 4:00 pm

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

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

i really dont have any idea how to solve this...please help...

Like this post

Source: Beat The GMAT — Problem Solving | Thu Dec 06, 2007 4:00 pm

Suyog: Master | Next Rank: 500 Posts; Posts: 315; Joined: Thu Aug 17, 2006 10:43 pm; Thanked: 23 times

by Suyog » Thu Dec 06, 2007 4:11 pm

Let a = 2, b = 5, a+b = 7

1. f(x) = x^2 so f(a) = 4, f(b) = 25 and a + b = 29
but, f(a+b) = 49, No

2. f(x) = x + 1 so f(a) = 3, f(b) = 7 and a + b = 10
but, f(a+b) = 9, No

3. N0

4. N0

5. f(x) = -3x so f(a) = -6, f(b) = -15 and a + b = -21
Similarly f(a+b) = f(7) = -21

ans E.

Like this post

bushra: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Tue Dec 04, 2007 10:32 am; Location: canada

thanks suyog

by bushra » Thu Dec 06, 2007 5:14 pm

thanks a bundle suyog...i aways have problem with these types of questions...have taken GMAT 2 weeks back...got 570...so am retaking again on jan 18....thanks again...

Like this post

moreonalps: Junior | Next Rank: 30 Posts; Posts: 15; Joined: Thu Oct 18, 2007 4:14 pm; Thanked: 1 times

by moreonalps » Tue Dec 18, 2007 7:48 pm

Is E the right answer..question is asking f(a+b)=f(a)=(b)

evaluating for E as per Suyog, f(a+b)=-21;f(a)=-6;f(b)=-15..so, how does f(a+b)=f(a)=f(b)..

Please explain..

Like this post

camitava: Legendary Member; Posts: 645; Joined: Wed Sep 05, 2007 4:37 amFollowed by: 5 members; Location: India; Thanked: 34 times

by camitava » Wed Dec 19, 2007 1:25 am

moreonalps, u r correct but in the Qs itself it is saying that f(a + b) = f(a) = f(b). It should be f(a + b) = f(a) + f(b). Oooppppppsssss! Ok! This is solely my understanding and I personally assume this from the solution offered by Suyog. Suyog, am I wrong?

Correct me If I am wrong

Regards,

Amitava

Like this post

Suyog: Master | Next Rank: 500 Posts; Posts: 315; Joined: Thu Aug 17, 2006 10:43 pm; Thanked: 23 times

by Suyog » Wed Dec 19, 2007 4:42 am

you are right Camitava..

I had solved something like this earlier while practicing....
and it was f(a+b) = f(a) + f(b)
So i solved considering that.. LOL

bushra, can u pls confirm the question...
Thanks guys!

Like this post

svijay800: Newbie | Next Rank: 10 Posts; Posts: 7; Joined: Wed Dec 19, 2007 11:02 pm; Location: Chennai, Tamil Nadu, INDIA

by svijay800 » Thu Dec 20, 2007 3:31 am

Should have been f(a+b) = f(a)+f(b) for sure, otherwise none of the choices will hold true

Like this post

Bschool08: Junior | Next Rank: 30 Posts; Posts: 11; Joined: Mon Dec 03, 2007 12:20 pm

by Bschool08 » Sun Dec 23, 2007 9:26 pm

Just as an FYI

https://www.beatthegmat.com/08app-t7424.html

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