{
Argument=x1,x2,x3
Fit_var=a0,a1,a2,a3,b0,b1,b2,b3
Expression=(a0+a1*x1+a2*x2+a3*x3)/(b0+b1*x1+b2*x2+b3*x3)
}
{
Argument=x1,x2,x3
Fit_var=a0,a1,a2,a3,a4,a5,a6,a7,a8,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9
Expression=(a0+a1*x1+a2*x2+a3*x3+a4*x1*x2+a5*x2*x3+a6*x3*x1+a7*x1*x1+a8*x2*x2+a9*x3*x3)/(b0+b1*x1+b2*x2+b3*x3+b4*x1*x2+b5*x2*x3+b6*x3*x1+b7*x1*x1+b8*x2*x2+b9*x3*x3)
}