YES Problem: -(-(neg(x),neg(x)),-(neg(y),neg(y))) -> -(-(x,y),-(x,y)) Proof: Matrix Interpretation Processor: dim=1 interpretation: [-](x0, x1) = x0 + 2x1 + 5, [neg](x0) = x0 + 1 orientation: -(-(neg(x),neg(x)),-(neg(y),neg(y))) = 3x + 6y + 29 >= 3x + 6y + 20 = -(-(x,y),-(x,y)) problem: Qed