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# challenge 25 QUESTION 22

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Manager
Joined: 05 Oct 2005
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31 May 2006, 13:37
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

function f (x) SATISFIES f (x) =f (x)^2 FOR ALL x which of the following must be true

f(4) = f(2)*f(2)
f(16) - f(-2) = 0
f(-2) + f(4) = 0
f(3) = 3*f(3)
f(0) = 0

THANKS
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best regards

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VP
Joined: 21 Sep 2003
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31 May 2006, 14:17
f (x) = f(x^2)
=> f(-2) = f(4) = f(16)
Hence f(-16) = f(-2)
or f(16)-f(-2) = 0.. which is B
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"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."

- Bernard Edmonds

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Senior Manager
Joined: 15 Mar 2005
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31 May 2006, 14:20
I am not sure if you really meant f(x) = f(x)^2 or f(x) = f(x^2), but I am going with the latter.

1. f(4) = f(2)*f(2)
RHS = f(2)*f(2) = f(2^2)*f(2^2) = f(4)*f(4)
f(4) = f(4)*f(4). Not true.

2. f(16) = f(2).
RHS=f(2) = f(2^2) = f(4) = f(4^2) = f(16) = LHS. True.

3. f(4) = f(-2)
RHS = f(-2) = f((-2)^2) = f(4) = LHS. True.

4. Not true.

5. Not true.
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VP
Joined: 29 Dec 2005
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31 May 2006, 16:57
kapslock wrote:
3. f(4) = f(-2)
RHS = f(-2) = f((-2)^2) = f(4) = LHS. True.

3. f(-2) + f(4) = 0
f(4) = - f(2)
rhs, = -f(2) = -f(2)^2 = - f(4) .... not true..

but why 5. f(0) = 0 is not true.

LHS = f(0)^2 = f(0).
are 0 and f(0) different?

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Manager
Joined: 18 Mar 2004
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03 Apr 2007, 14:36
I understand why B is correct, but why isn't E also correct?

LHS = f(0^2) = f(0)
RHS = 0

0=0 correct.

Thanks

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Intern
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22 Jul 2007, 05:30
Just wanted to say Hey,

I think we're at the same point in our studies. I've just finished the MGMATs and have taken 2 Challenges.

If you ever need to break down and discuss more of the test. Let me know. . .

MWW7786
Tallahassee, FL

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MWW7786   [#permalink] 22 Jul 2007, 05:30
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# challenge 25 QUESTION 22

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