YES Problem: p(s(x)) -> x fac(0()) -> s(0()) fac(s(x)) -> times(s(x),fac(p(s(x)))) Proof: Matrix Interpretation Processor: dim=2 interpretation: [1 0] [times](x0, x1) = [0 0]x0 + x1, [2 2] [0] [fac](x0) = [1 0]x0 + [3], [3] [0] = [0], [1 0] [p](x0) = [1 0]x0, [1 1] [s](x0) = [2 2]x0 orientation: [1 1] p(s(x)) = [1 1]x >= x = x [6] [3] fac(0()) = [6] >= [6] = s(0()) [6 6] [0] [5 5] [0] fac(s(x)) = [1 1]x + [3] >= [1 1]x + [3] = times(s(x),fac(p(s(x)))) problem: p(s(x)) -> x fac(s(x)) -> times(s(x),fac(p(s(x)))) Matrix Interpretation Processor: dim=2 interpretation: [1 0] [2 0] [times](x0, x1) = [2 0]x0 + [0 0]x1, [1 2] [1] [fac](x0) = [2 0]x0 + [0], [1 0] [1] [p](x0) = [1 0]x0 + [0], [1 1] [0] [s](x0) = [3 3]x0 + [3] orientation: [1 1] [1] p(s(x)) = [1 1]x + [0] >= x = x [7 7] [7] [7 7] [4] fac(s(x)) = [2 2]x + [0] >= [2 2]x + [0] = times(s(x),fac(p(s(x)))) problem: Qed