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2015-01-29 00:03:45 +0200 asked a question Cannot desolve ODE

I'm trying to compute the solution for a first order differential equation using the code below:

var('g, a, v_e, m_0, v_9, k')
m(t) = (m_0 - a*t)
v = function('v', t)
de = m*diff(v, t) == -v_e*diff(m, t) - k*v - m*g
ans = desolve(de, v, ics=[0,0], ivar=t)

This returns the following error: TypeError: Computation failed since Maxima requested additional constraints; using the 'assume' command before evaluation may help (example of legal syntax is 'assume(-k/a>0)', see assume? for more details)

Running assume(-k/a>0) before desolve does not remove the error. This error does not happen with the k*v term removed. By hand, I was able to solve this DE using integrating factors.