I need help to find critical points of the function: $$f(x,y,z)={(x^2+2y^2+3z^2) e ^{-(x^2+y^2+z^2)}}$$ Then I have to classify these critical points as local maxima/minima or saddle points.
What I would do is to take the partial derivatives $\frac{\partial f}{\partial x}(x, y, z)$, $\frac{\partial f}{\partial y}(x, y, z)$ and $\frac{\partial f}{\partial z}(x, y, z)$.
But now I will get
$\frac{\partial f}{\partial x}(x, y, z)$ = $ {2x-6e^{-x^2-y^2-z^2}xz^2} $
$\frac{\partial f}{\partial y}(x, y, z)$ = $ {4y-6e^{-x^2-y^2-z^2}yz^2} $
$\frac{\partial f}{\partial z}(x, y, z)$ = $ 3(-2e^ {-x^2-y^2-z^2}z^3+2e^{-x^2-y^2-z^2}z) $
Normally I would put them in the matrix form and solve the system of equation for x, y and z.
But I don't know how to solve the system of equation with these partial derivatives. What I am doing wrong or what should be done in order to solve this problem?