Question about the constrained quadratic problem

[jdumas]

SeamAwareDecimater/cost_and_placement.cpp

Line 194 in c699343

// The unknowns are x,y,z,u0,v0,u1,v1,1

Hi guys. Looking at the code of the quadratic problem, I was wondering why do you use the constant 1 as one of the unknown variable (through an equality). Is it there for numerical reasons, or something else?