x = var('x')
y = function('y',x)
deq1 = diff(y,x,3)-diff(y,x,2)+100*diff(y,x)-100*y==0
soln = desolve_laplace(deq1 ,  [y,x] , ics=[4,11,-299])
soln

*shankar ,student ,Pydah college of eng...