Pedal with respect to the origin of Folium of Descartes

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How can one calculate the pedal curve with respect to the origin of the Folium of Descartes,

$x^3+y^3-3axy=0$.

Note that an implicit curve is desired, not its parametrization. I already know how to calculate a pedal curve, however the pedal to this curve has escaped my grasp to compute. I know the answer should be

$a^2 (3 a^2 x^2 y^2 + 6 x y (x^2 + y^2)^2 + 4 a (x^5 + x^3 y^2 + x^2 y^3 + y^5)) = (x^2 + y^2)^4$

But how do you compute this?

I got as far as

$\frac{x_0^2-ay_0}{ax_0y_0} = \frac{\cos(\theta)}{r}$

and

$\frac{y_0^2-ax_0}{ay_0x_0} = \frac{\sin(\theta)}{r}$

Where $x_0$ and $y_0$ are points that are in the curve, meaning

$x_0^3+y_0^3 -3ax_0y_0 = 0$

And $r$ and $\theta$ are the polar form of the pedal curve.