Thank you for the response I tried using Dot in QT and QB since later on everything comes as X QL=0 and we get co-eficients from X.. QR = [Lambda]1 QL ; QB = QT;

FL = DLL QL + DLR QR + DLT.QT + DLB .QB; eq[5] = DRL QL + DRR QR + DRT.QT + DRB .QB + [Lambda]1 FL;

[Lambda]2 = 1 FT = DTL QL + DTR QR + DTT.QT + DTB.QB eq[6] = DBL QL + DBR QR + DBT.QT + DBB.QB + [Lambda]2 FT eq[7] = Collect[eq[6], QL] QT = E1.(DBL + DBR [Lambda]1 + DTL [Lambda]2 + DTR [Lambda]1 [Lambda]2) eq[8] = DRL QL + DRR QR + DRT.QT + DRB .QB + [Lambda]1 FL QL = 1 (QL here i treated as some number since the the equation is X QL=0, where X=eq8] eq[10] = Collect[Expand[eq[8]], [Lambda]1]

i am getting the result as DRL + DLR [Lambda]1^2 + [Lambda]1 (DLL + DRR + DLB.E1.(DBL + DTL + DBR [Lambda]1 + DTR [Lambda]1) + DLT.E1.(DBL + DTL + DBR [Lambda]1 + DTR [Lambda]1)) + DRB.E1.(DBL + DTL + DBR [Lambda]1 + DTR [Lambda]1) + DRT.E1.(DBL + DTL + DBR [Lambda]1 + DTR [Lambda]1).

This result is not expandable. Expand command gives me the same result. So how to get the co-ffiecient after that