dx1/dt=-p4*x1+p1/(p2+x3^p3);
dx2/dt=p5*x1-p6*x2;
dx3/dt=p7*x2-p8*x3;
y1=x1;
y2=x2;
y3=x3;
x1(0)=0.3;
x2(0)=0.9;
x3(0)=1.3

