Hi there. I've got this function , and I have to analyze what happens at in terms of maxims and minims. But what I actually have to proof is that theres a saddle roof at that point.
Theres is a critical point at . Lets see:
Its clear there that there is a critical point at
The determinant of the partial derivatives of second order at
Then I can't say anything from there. And actually, if I try at any line that passes through I would find a minimum. I know that it isn't a minimum, but I don't know how to prove it.