Explanation regarding CreateTangentEquations function

[AlexYiningLiu]

Can you please explain the motivation behind these 2 lines of code in CreateTangetEquations? Specifically, why the multiplication of iy and iyA by the xres value? Thanks.

RNPolynomial d(1.0, (iy)*xres+(ix), 1.0);
RNPolynomial dA(1.0, (iyA)*xres+(ixA), 1.0);