I have three variables $X, Y, Z$ whose functional form is the following (I also have a function for $Z$ which is somewhat complicated but is not essential for my question here; so it is omitted.):
$X=a+bY$
$\dot{Y}=c+dZ$
where $a,b,c,d$ are abstract parameters, and the overdot refers to time derivative of the variable, i.e. $\frac{dY}{dt}$.
Setting aside an obvious fact that this system is reduced to $\dot{X}=\dot{Z}$, I would like to know the Mathematica code for this system. For the first equation, I have
X[Y_] := a + b*Y
But I am stuck with the second one. Do I have to make the variables a function of time t
? But in that case, doesn't the system become discrete, not continuous?