Find the stationary points for the surface. And find the local and absolute maxima or minima for the following function.

Is there any stationary points for this surface?

Let z = f(x,y)

I found the

=

and

=

I'm supposed to equate the two equations to get the stationary points (X , Y) and substitute them into f(x,y) to get Z. But I could not since I could only get from the two equations and that's it.

How do I proceed? Did i do anything wrong?