public class Funcion extends Ecuacion{
  double a;
  double n0;
  double b;
  final double k=0.46235;
  public Funcion(double r0, double n0) {
    this.b=16*Math.PI*k*r0*r0/(3*n0);
    this.n0=n0;
  }
  void setMoles(double n){
    this.a=n/n0;
  }
  public double f(double x){
        double y=x*x*x*x*x*x*x+b*x*x*x*x*x*x-a*x*x*x*x-b;
        return y;
    }
}
public class MiCanvas extends Canvas {
    final double r0=42.06;  //radio inicial
    final double n0=12.5; // número inicial de moles
    double r=r0;
    double xEmbolo=1.0;
    Funcion f=new Funcion(r0/100, n0);
    int nVeces;
    double nMoles;
//....

  void mover(){
    xEmbolo+=0.01;
    nMoles=n0+nVeces*5+xEmbolo*5;
    f.setMoles(nMoles);
    r=r0*f.puntoMedio(1.0, 5.0); //radio del globo
  }
//...