Ok, so the original function is

and the problem is to find the derivative with respect to x, respect to y, respect to xx, respect to yy, and respect to xy/yx and find the critical numbers as well as any relative extrema or saddle point if applicable.

I found that the derivative with respect to x is

, the derivative with respect to y is

, the derivative with respect to xx is

, the derivative with respect to yy is

and finally the derivative with respect to xy is

.

Now, I tried setting

from

equal to

from

but that didn't work. I tried doing substitution for

and

but that ends up being 1=4 which obviously isn't true nor is it a CN...so how would I find the CN's for this problem? I'm sure I'm overlooking something simple, however, I can't find out what that simple thing is.