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# challenge 25 QUESTION 22

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Manager
Joined: 05 Oct 2005
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challenge 25 QUESTION 22 [#permalink]  31 May 2006, 13:37
plz explain your reasoning
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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VP
Joined: 21 Sep 2003
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[#permalink]  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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Senior Manager
Joined: 15 Mar 2005
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[#permalink]  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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[#permalink]  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?
Manager
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[#permalink]  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
Intern
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MWW7786 [#permalink]  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
MWW7786   [#permalink] 22 Jul 2007, 05:30
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# challenge 25 QUESTION 22

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