Given a function f: R^2 -> R of class C^3 with a critical point c.
Why CANNOT the hessian matrix of f at point c be given by:
The Attempt at a Solution
So first i want to clarify this.
When it says f: R^2 -> R, that means the function is of two variables (x and y)?
And when it says class C^3 that means the third derivative of the function exists and is continuous. So would a function be x^3 or x^4? the third derivative would be 24x for x^4 and is continuous. The third derivative of x^3 would be 6.
I'm not sure about the answer..