Should the critical points belong to the domain of $f$?

34 Views Asked by At

If $f(x,y) = x ^2 + xy + y^2 - 4 \ln x - 10 \ln y,$ and I found the critical points to be {(1,2), (-1,-2),$(4/\sqrt{3}, -5/\sqrt{3})$, $(-4/\sqrt{3}, 5/\sqrt{3}) $} .... should I exclude the points containing negative values of $x$ & $y$ because they do not belong to the domain of the function?

1

There are 1 best solutions below

0
On BEST ANSWER

Yes, you should exclude these points, since the domain of $f$ is $\{(x,y) \in \mathbb R^2: x >0,y>0 \}.$