$$f(x,y) = 2x^{4} - 3x^{2}y + y^{2}$$

I found the stationary points of this function using the equations -

$$\frac{\partial f}{\partial x} = 0 \qquad \frac{\partial f}{\partial y} = 0$$

I got $(0,0)$.

Now we calculate $R$, $S$, and $T$ at $(0,0)$ where 

$$R = \frac{\partial^{2} f}{\partial x^{2} } \qquad
S = \frac{\partial^{2} f}{\partial x\partial y} \qquad
T = \frac{\partial^{2} f}{\partial y^{2} }$$

then, 
$$RT - S^{2} = 0$$

This does't lead to any result. How to find nature of this stationary point?

I know what local minima, local maxima, and saddle points are, but how to find the nature of $(0,0)$?