Hi @Gan Huang
Since 
is known, you can make direct substitutions into 
and 
. Here is the demo:
is known, you can make direct substitutions into and . Here is the demo:function Demo_ode45
close all
clc
tspan = [0 1]; % time span of simulation
y0 = [1 0.5 0.25]; % initial values
[t, y] = ode45(@(t, y) odefcn(t, y), tspan, y0);
plot(t, y, 'linewidth', 1.5)
grid on
xlabel('Time, t [sec]')
ylabel('x, y, z')
title('Time responses of the system')
legend('x', 'y', 'z', 'location', 'best')
end
function dydt = odefcn(t, y) % Ordinary Differenctial Equations
dydt = zeros(3,1);
dydt(1) = 6*y(1)/y(2);
dydt(2) = 4*(6*y(1)/y(2));
dydt(3) = 16*(6*y(1)/y(2));
end
Result:
