I am trying to implement the two-stage Runge-Kutta method of the fourth order for solving a system of differential equations, but an error occurs at the stage of solving the system of equations. NSolve, Solve, FindRoot didn’t work for me. Where am I making a mistake?
Your NDSolve code seems to work fine. Why do you think there is a problem with the NDSolve solution? I don’t understand why you want to implement your own integration when Mathematica already has most techniques built in if you set the Method properly.