I get one simulation with only one expression below:

the P(t) and Q(t) with their derivative are the expected, all the R，C are known parameters.

suppose the initial values are known ,but I don’t know how to define the ode in julia for using ODEProblem() . please share some suggestions.

thanks.

I think this is rather a mathematical question than a Julia question, and perhaps a homework question at that? Can you rewrite the equation as a system of equations where the left-hand side only contains therms like \frac{d X(t)}{d t} and the right hand side doesn’t contain time derivatives (i.e. only terms like X(t))? You may need to introduce auxiliary variables. Once you’ve managed that, setting up the `ODEProblem`

should be easier. Good luck!

thanks, I solved it.