# Determine max of $2$ parameter functions

If I have $2$ functions $f(x)$ and $f(y)$, may I determine a function $f(x,y)$? My purpose is to determine $\max(f(x,y))$ if I know $f(x)$ and $f(y)$.

Thank you!

PS: Sorry for my english!

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May I ask to add me any example here. It is good to know your conditions for two functions and... – Babak S. Jan 12 at 8:11
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