[a, b, c, d] = euler_explicit(@(x, y) 3*exp(-201*x) - 5*exp(-x), @(x, y) -201*y - 1000*exp(-x), -2, 0, 1, 0.009);
[e, f, g, h] = euler_implicit(@(x, y) 3*exp(-201*x) - 5*exp(-x), 201, -2, 0, 1, 0.01);

[T,Y] = ode15s( @(x, y) -201*y - 1000*exp(-x),[0:0.01:1],-2);

t = 0:0.01:1;
j = 3*exp(-201*t) - 5*exp(-t);

hold all;

plot(t,j);
plot(c,d);
plot(g,h);
plot(T,Y);

legend('Analytical','Explicit','Implicit','ODE15S');