Find the set of global minimizers of f?
Does f have a global maximizer?Justify?
I first calculated the gradient of f and then let partial derivative of x and y to be equal to 0.
Thereby the critical points I found are (0,0)(0,3)(0,-3)(6,0)(6,3)(6,-3).
I think a global maximizer doesn't exist as when limit of function goes to infinity from both x and y ,function goes to infinity.
But how to find if global minimizers are there?