Hi. I have an inequalities system: x1 < x < x2 y1 < y < y2 -w < a*x + b*x < w -h < -b*x + a*y < h I need to check (a, b, x1, x2, y1, y2, w, h) and say if there is an (x, y) pair that makes all inequalities above true. I''ve been having some ideas, but I''d like to hear you out. Oren (http://qsoft.cjb.net). p.s. If anyone can guess what''s the visual meaning of those inequalities together I''ll tell him: Good for you.