It depends on what you want to do, and what the left-hand side actually is. Is the function ‘rT’ or ‘T( r )’?
In the Symbolic Math Toolbox:
syms D L P rT(r)
Eqn = diff(rT) == D*P/L * r;
This assumes that ‘rT’ is a separate function. I have no idea what you are actually doing.
If ‘T’ is the function:
syms D L P r T(r)
Eqn = diff(r*T) == D*P/L * r;
However it may not be possible to integrate it, since the initial condition of ‘T(0)’ implies that ‘r’ is 0 and the integrated differential equation would be infinite at 0.
