hi

is the following function concave or convex:

f{x,y,z} = x*y + z

I tried to find the hessian of this but it is coming out to be 0 which means that the Hessian test doesnt say anything about convexity or concavity. So, is there any other method that can be used which can give conclusive results?

Thanks

(p.s. MF rocks as always thanks guys for ur replies to all my posts! )