appendix:'example'
part1: enriching-section 'operating line',revision1
peter.vlasschaert@gmail.com,05/04/2017

float(0.501+4.5*0.43-5.5);

m:0.504;
b:0.43;
alpha :5.5;

A:(alpha-1)*m;
B:m+(alpha-1)*b-alpha;
C:b;

p1:A+B+C;

p2:p1-A-C;

p3:A+C;

assume : b > 0 ,because -(A+C) < 0

p4:-(A+C);