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Positively Real (Posted on 2012-09-09) Difficulty: 3 of 5
R+denotes the set of positive real numbers.

Determine all possible functions f:R+ R+ such that:

f(f(x)) = 12x - f(x) for all x > 0.

No Solution Yet Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Hints/Tips Possible Answer | Comment 1 of 4

f(x) = -4x

f(x) = 3x

I think these may be the only solutions.  I have a way of showing why and will present when I have more time.

  Posted by Chris, PhD on 2012-09-09 18:44:18
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