zoki85
Jun4-07, 02:16 PM
Let f(x,y) be a real valued function defined for all positive x,y.
If f(x,y)=f(y,x) and
\frac{\partial^2 f}{\partial x^2}=y+1
and
\frac{\partial^2 f}{\partial y^2}=x+1
are we allowed to conclude than:
f(x,y) is convex on X\times Y=<o,+\infty>\times <o,+\infty> ?
I think this is trivial question for experts but I don't know how to prove/disprove this.
If f(x,y)=f(y,x) and
\frac{\partial^2 f}{\partial x^2}=y+1
and
\frac{\partial^2 f}{\partial y^2}=x+1
are we allowed to conclude than:
f(x,y) is convex on X\times Y=<o,+\infty>\times <o,+\infty> ?
I think this is trivial question for experts but I don't know how to prove/disprove this.