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

Redeem

Another question from MGMAT guide

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 59
Joined: Wed Mar 24, 2010 9:24 am
Thanked: 4 times
Followed by:2 members

Another question from MGMAT guide

by sch » Tue May 04, 2010 6:16 pm
For which of the following functions does F(x)=F(2-x)

Answer is f(x)=2x-x^2 They solved it by plugging in 4. But that yeilds -8 for F(x) and -6 for F(2-x).

I cant figure out how that can be an answer when the values are different in each functions, and they are clearly not equal to eachother. I am a little slow in math and even simple problems like these are a challange for me, if anyone can explain me how this is an answer I would greatly apriciate it.
Top
Source: — Quantitative Reasoning |
User avatar
Master | Next Rank: 500 Posts
Posts: 214
Joined: Mon Mar 29, 2010 1:46 pm
Location: Houston, TX
Thanked: 37 times
GMAT Score:700

by sk818020 » Tue May 04, 2010 6:50 pm
They were right

F(x)=F(4)=

2(4)-4^2= 8-16 = -8

F(2-x)=F(2-4)=F(-2)=

2(-2)-(-2)^2 = -4-4 = -8
Top
User avatar
Legendary Member
Posts: 526
Joined: Sat Feb 21, 2009 11:47 pm
Location: India
Thanked: 68 times
GMAT Score:680

by harshavardhanc » Wed May 05, 2010 12:26 am
sch wrote:For which of the following functions does F(x)=F(2-x)

Answer is f(x)=2x-x^2 They solved it by plugging in 4. But that yeilds -8 for F(x) and -6 for F(2-x).

I cant figure out how that can be an answer when the values are different in each functions, and they are clearly not equal to eachother. I am a little slow in math and even simple problems like these are a challange for me, if anyone can explain me how this is an answer I would greatly apriciate it.
another way to go about it :

as f(x) = 2x - x^2

or x [ 2 - x ] (taking x common )

now, if you put (2-x) in place of x or if you try to find out f (2-x), you'll get :

(2-x) [ 2 - (2-x) ]

= (2-x) [ 2- 2 + x ]

= x (2-x)

which is equal to f (x). You've got your answer.

HTH.
Regards,
Harsha
Top
Post new topic Post Reply
• Page 1 of 1