Thanks for your reply!
I already tried it with Collect[], unfortunatly I have two input variables U = {F, p} and I dont know how to collect only those results containing U.
Collecting F(x) is no issue, I set F and p to zero, but I relly don't know how to collect my Matrix B -> xdot = F(x)+B(x)U
I somehow need to erase the other terms for collecting B, its too large for copy, paste it... Btw my system has order 8.
For any advice I would be very grateful
