YES O(n^5) TRS: {a(b(a(x))) -> b(a(b(x)))} DUP: We consider a non-duplicating system. Trs: {a(b(a(x))) -> b(a(b(x)))} Matrix Interpretation: Interpretation class: triangular [X4] [1 0 0 0 1][X4] [0] [X3] [0 0 0 0 0][X3] [0] [a]([X2]) = [0 0 0 0 0][X2] + [0] [X1] [0 0 0 0 0][X1] [1] [X0] [0 0 0 0 0][X0] [1] [X4] [1 0 0 0 0][X4] [0] [X3] [0 0 0 0 0][X3] [0] [b]([X2]) = [0 0 0 0 0][X2] + [0] [X1] [0 0 0 0 0][X1] [0] [X0] [0 0 0 0 1][X0] [0] Qed