- #1
ritwik06
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Homework Statement
If f'(x)>0 for all real positive x, where f:R+ ---> R and
f(x)+(1/x)=f-1(1/(f(x))),
f-1(1/(f(x)))>0 for all x>0. Find all the possible values of (i) f(2),(ii) f'(2) and (iii) Limit (x f(x)) as x ----->0 .
The Attempt at a Solution
Guessing from the last part, I intuitively, took f(x) = k/x. Using this, I get a quadratic in k which yields that k might be [tex]\frac{1 (+/-) \sqrt{5} }{2}[/tex]. But this was just a guess. And there might still be other functions which satisfy that equation. I wonder if they could be manually solved for.
All that I need from you guys is to check out if all the possible solutions of this equation can be solved manually or not. If not, please let me know how can I get solutions to this equation using a Computer Algebra System. Actually, I have both Matlab R2008a and Mathematica 7 but I don't know how to use them to solve functional equations involving inverses. If anyone of you could provide me the syntax for these CAS on how to solve functional equations, I shall be very grateful.
Thanks.
Ritwik