Can someone give me advice on this brain scrambler?

6x-8 is the output, but I must find f(x) in order to input f(f(x)) to create such an output.

Any ideas on how to tackle this problem?

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- Dec 10th 2018, 05:51 PM #1

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- Dec 10th 2018, 05:54 PM #2

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- Dec 10th 2018, 06:24 PM #3
## Re: f(f(x)) problem

I would assume $\displaystyle f(x)$ is linear:

$\displaystyle f(x)=ax+b$

And then:

$\displaystyle f(f(x))=a(ax+b))+b=a^2x+(a+1)b=6x-8$

Equating coefficients, we then have:

$\displaystyle a^2=6$

$\displaystyle (a+1)b=-8$

Can you proceed?

- Dec 10th 2018, 07:18 PM #4

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