For comparison with other CAS choose from: Axiom Derive Macsyma Maple Reduce
Solve[ alpha c1 -beta c1 ^2 -gamma c1 c2 +epsilon c3 == 0,
-gamma c1 c2 + (epsilon+theta) c3 - eta c2 == 0,
gamma c1 c2 + eta c2 - (epsilon+theta) c3 == 0 ,
c3,c2,c1 ]
{{c3 -> (c1 (-alpha + beta c1 -
alpha c1 epsilon gamma
---------------------------- +
epsilon eta - c1 gamma theta
2
beta c1 epsilon gamma
---------------------------- -
epsilon eta - c1 gamma theta
alpha c1 gamma theta
---------------------------- +
epsilon eta - c1 gamma theta
2
beta c1 gamma theta
----------------------------)) / epsilon,
epsilon eta - c1 gamma theta
c2 -> (c1 (alpha epsilon - beta c1 epsilon +
alpha theta - beta c1 theta)) /
(-(epsilon eta) + c1 gamma theta)}}
Simplify[%]
c1 (-alpha + beta c1) (eta + c1 gamma)
{{c3 -> --------------------------------------,
epsilon eta - c1 gamma theta
c1 (alpha - beta c1) (epsilon + theta)
c2 -> --------------------------------------}}
-(epsilon eta) + c1 gamma theta