View Full Version : Functions on GMAT
 
 AWR83
Dec 27, 2008, 12:06 PM
for which of the following functions is f(x)=f(x-1)?
a) f(x)=x^2(1-x)^2
b) f(x)=1-x
c) f(x)=1-x^2
 
Thanks,
 v1033
Dec 31, 2008, 11:20 AM
why don't you try putting some specific examples into the functions?
 
e.g.
 
a) f(2) = 4 x 1 = 4
    f(2-1) = 1 x 0 = 0
so a doesn't satisfy f(x)=f(x-1)
 v1033
Dec 31, 2008, 11:21 AM
Or do I misunderstand the question?
 EuRa
Jan 4, 2009, 10:04 AM
You simply substitute the equations:
 
For example, in B we have f(x)=1-x, substituted gives you 1-(x-1), which = 1-x+1 = 2-x.  So this isn't the answer.
 
-----
 
This question is actually a very popular question to give, but it's always f(x) = f(1-x), and the answer would be A.  Are you sure you wrote it the right way?  Because I did all A, B, and C, and none of them worked.  Are there more choices?  Did you write it correctly?
 v1033
Jan 4, 2009, 10:28 AM
Eura,I don't see why the reddie my answer is not wrong merely incomplete and I thought we were meant to give pointers not answers.
 
Awr83, I agree with eura's last point I also think none of them work and you may have posted an incorrect or incomplete question...
 EuRa
Jan 4, 2009, 10:52 AM
eura,i don't see why the reddie my answer is not wrong mearly incomplete
Even if it is incomplete, it's going in the wrong direction.  I don't mean to be a negative nancy, but I am a High School Math Teacher and I taught this lesson not even 3 weeks ago.
 v1033
Jan 4, 2009, 10:55 AM
Then you may know of john mason's research that when stuck on a maths problem; specialising can help you on the way to generalising, which was the direction I was going in...
 EuRa
Jan 4, 2009, 07:25 PM
I was in a bad mood when I wrote all this earlier.  Your way (using examples) will work just fine.
 
I'll give you 2 positives to counter the negative comment.