Cooperation factor: In facsimile systems, the product of the total scanning length and the scanning density, given by CF = L σ, where L is the scanning line length[?] and σ is the scanning line density, both in compatible units.
Note: For example, a 20-cm line and a line density of 6 scanning pitches per centimeter would yield a cooperation factor of 120.
... because it discriminates between three qualitatively different cases:
If the discriminant is zero, then there is a repeated solution x, and this solution is real. ...