Functional Equation [Own]

For discussing Olympiad Level Algebra (and Inequality) problems
Corei13
Posts:153
Joined:Tue Dec 07, 2010 9:10 pm
Location:Chittagong
Functional Equation [Own]

Unread post by Corei13 » Tue Sep 20, 2011 12:05 pm

Find all continuous function $f:\mathbb{R} \rightarrow \mathbb{R}$ such that,
\[ f(xf(y) + yf(x) )= f(f(xy)) \]
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Corei13
Posts:153
Joined:Tue Dec 07, 2010 9:10 pm
Location:Chittagong

Re: Functional Equation [Own]

Unread post by Corei13 » Sat Nov 19, 2011 12:45 pm

At last solved :mrgreen:

Complete solutions:
$ f(x) =\begin{cases}c &\mbox{if }x\geq a\\ a+h(x) &\mbox{if }a\geq x\geq\frac{r}{2a}\\ \frac{r}{2x}+h(x) &\mbox{if }\frac{r}{2a}\geq x\end{cases} $


Where $ 2c^{2}\geq 2ac\geq r\geq a $ and $ h:(0,a]\longrightarrow [0,\infty) $
is any continuous function with $h(a)=c-a$.
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Corei13
Posts:153
Joined:Tue Dec 07, 2010 9:10 pm
Location:Chittagong

Re: Functional Equation [Own]

Unread post by Corei13 » Tue Nov 22, 2011 2:34 am

Complete Solution,
Attachments
soln.pdf
(68.18KiB)Downloaded 216 times
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