A method of fitting a curve to data points so as to minimize the sum of the squares of the distances of the points from the curve.
For example (yei,x1i,x2i,x3i,x4i) is experimental data and relevant function is y=f (x1,x2,x3,x4), some unnkown parameters
(a1,a2,a3,a4) can be solved by minimizing the sum of squares of residues.
Tr:=sum(f, i = k .. n);
da1:=diff(Tr, a1);da2:=diff(Tr, a2);da3:=diff(Tr, a3);da4:=diff(Tr, a4);