“…Recently, the study of cancellation problem has been revitalized for noncommutative algebras thanks to [BZ1], which mainly employs the famous Makar-Limanov invariants [Ma1,Ma2] and the noncommutative discriminants as investigated in [CPWZ1,CPWZ2]. It is usually very difficult to describe the discriminant for a given algebra; fortunately, many useful results on discriminants have been further established in [BY,CYZ1,CYZ2,GKM,GWY,NTY,WZ]. Ever since [BZ1], there has been much progress made in the study of cancellation problem for noncommutative algebras [BZ2,CYZ1,Ga,LR,LY,LeWZ,LuWZ,LMZ,Ta1,Ta2,TRZ].…”