YES O(n^4) TRS: {*(x, *(minus(y), y)) -> *(minus(*(y, y)), x)} DUP: We consider a non-duplicating system. Trs: {*(x, *(minus(y), y)) -> *(minus(*(y, y)), x)} Matrix Interpretation: Interpretation class: triangular [X3] [1 0 0 0][X3] [1] [X2] [0 0 0 0][X2] [0] [minus]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X7] [X3] [1 0 1 0][X7] [1 0 1 0][X3] [0] [X6] [X2] [0 0 1 0][X6] [0 0 0 0][X2] [0] [*]([X5], [X1]) = [0 0 1 0][X5] + [0 0 1 0][X1] + [1] [X4] [X0] [0 0 0 1][X4] [0 0 0 1][X0] [0] Qed