maths
posted by Zane .
find the general solution of the following first order differential equation.
u(t): du/dt = u /t+2t
pls show all working

I assume you mean
du/dt = (u/t) + 2t and not
u/(t + 2t) = u/(3t)
Your D.E. is of the form
du/dt + Pu = Q
where P = 1/t and Q = 2t
The method of "integrating factors" can be used. Your textbook should have an explanation of the method.
There is a function rho(t) given by
rho(t) = exp(integral of P(t)dt)
such that the solution is
rho(t)*u
= integral of (rho*Q) + C