Literally a one line code:
NDSolve[{x'[t] == x[t] + 3, x[0]==3, x'[0]==3}, x[t], {t, 0, 10}]
It shows me the error, that:
NDSolve : Equation or list of equations expected instead of True in the first argument {True,x[0]==3,False}.
Why does Mathematica interpret my equation as "true", and my second initial condition as "false"?
I am really desperate, I can't find a solution to that at all anywhere on the internet. Even using "ClearAll["Global`*"]" doesn't do ANYTHING
sol=x[t]/.NDSolve[{x'[t]==x[t]+3,x[0]==3},x[t],{t,0,10}][[1]]; Plot[sol,{t,0,10}]and I get a plot of your result. Try EXACTLY those steps and see what you get. I didn't give it two conditions because a first order ODE expects one condition. Does this work for you? – Bill Oct 15 '22 at 21:53=instead of==in a couple of places. If so, it can be fixed as shown in a couple of the answers. Note that it is explained there why ``ClearAll["Global`*"]` does not fix this problem. – Michael E2 Oct 16 '22 at 01:27