Function f(x) satisfies f(x) = f(x^2) - PS (>700)

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GMAT_ClubMBA
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Registrado: 03 Jun 2011, 14:29

Function f(x) satisfies f(x) = f(x^2) - PS (>700)

Mensaje por GMAT_ClubMBA »

If a function f(x) satisfies for every x, which of the following must be true?

A)

B)

C)

D)

E)
respuesta: show
B

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Luke
Asociado Senior
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Registrado: 26 Sep 2011, 18:49

Re: Function f(x) satisfies f(x) = f(x^2) - PS (>700)

Mensaje por Luke »

This question can be a bit tricky!

I tried by using examples, but we must be careful because the equality is valid for every x, so you can't use any function to check the options!

However, we can write down several equations to facilitate the checking option by option, for example:
f(4)=f(16)
f(2)=f(4)
f(-2)=f(4)
f(1)=f(1)
f(0)=f(0)
f(3)=f(9)

With that we can easily rule out the third last options. We can also rule out option A, because f(4)=f(2) <> f(2)*f(2). Then, option B is correct (f(-2)=f(4)=f(16))

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