plotting two equations?

So i need to plot 4*x-x*y^2 = 5 and (1/3)*x^3+y^2 = 1 between x = -10 .. 10, y = -10 .. 10.

I tried:

> f := 4*x-x*y^2 = 5;
                         
> g := (1/3)*x^3+y^2 = 1;
                       

   > plot({f, g}, x = -10 .. 10, y = -10 .. 10)

What did i do wrong?

Thanks