Find the following.
\[f_x, f_y, f_{xx}, f_{yy}, f_{xy} and f_{yx} \]
\[ f(x,y) = \frac {x} {y} \] \[ f_x = \frac{1}{y} \]
\[ f_y = \frac{-x}{y^2} \]
\[ f_{xx} = 0 \]
\[ f_{yy} = \frac{-2x}{y^3} \]
\[ f_{xy} = \frac{-1}{y^2} \]
\[ f_{yx} = \frac{-1}{y^2} \]