function dx=preypredator(t,x)
%dy=preypredator(t,y,par)
%computes the right-hand side of the Lotke-Volterra system
a=1;%the constants are chosen so that the stable point is [100;10];
b=0.1;
c=1;
d=0.01;
dy=[a*y(1)-b*y(1)*y(2);-c*y(2)+d*y(1)*y(2)];%Lotke-Volterra