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