On 03/09/2013 11:14 PM, Paul J. Ste. Marie wrote: > cx = -((b^2-1)*y2+(1-b^2)*y1-2*b*x2-2*b*x1)/(4*b okay let's try: display2d : false; h :-((b^2-1)*y2+(1-b^2)*y1-2*b*x2-2*b*x1)/(4*b); h : ratsubst(b2m1,b^2-1,h); h : factorsum(h); Andre