function [Ydot] = chemostat(t,Y)
a1=2; a2=3;
Ydot(1) = a1*(Y(2)/(1+Y(2)))*Y(1)-Y(1);
Ydot(2) = -Y(2)/(1+Y(2))*Y(1)-Y(2)+a2;
Ydot=Ydot';