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Hi, Could some body help me here, Am trying to use dsolve to solve the following system of equations but I am getting the following error

difS := diff(w(t), t) = nu+delta*z(t)-(1/100)*psi*w(t)*(x(t)+epsilon*y(t))-mu*w(t);

difI := diff(x(t), t) = (1/100)*(1-rho)*psi*w*(x(t)+epsilon*y(t))+PI*y(t)-h[1]*x(t);

difC := diff(y(t), t) = (1/100)*rho*psi*w*(x(t)+epsilon*y(t))+(1-q)*eta*x(t)-h[2]*y(t);

difR := diff(z(t), t) = q*eta*x(t)+beta*y(t)-(mu+delta)*z(t)

Why do I get this error message:


X := proc (a, b) local w, V, i, E, s; global Nr, sampvar, u;

w := sampvar*(1-a-b);     V[2] := u[1]^2;

if w = 0 then w := 0.1e-4 end if;

for i from 3 to Nr-1 do V[i] := w+a*u[i-1]^2+b*V[i-1] end do;

for i from 2 to Nr-1 do E[i] := -(1/2)*ln(V[i]^2)-u[i]^2/V[i] end do;

s[1] := 0;   for i from 2 to Nr-1 do s[i] := s[i-1]+E[i] end do;

s[Nr-1]

end proc:

I hope to know

what the meaning of the follwing message

illegal use of a former parameter

restart; with(Statistics)

#Define:

A := RandomVariable(Geometric(p))+1; F := Mean(A);M := abs(A-F)/A;

#and ask Maple to find a pdf of the r.v. M:

f := `assuming`([PDF(M, x)], [x > 0])

#Maple 15 gives an answer, but what does it mean by the output for this input

subs(p = 1/3, x = 3, f)

#or how do I plot this pdf of M? Does Maple give a correct answer?

# Why does the error message appear when I do subs(p = 1/3, x < 3, f...