clear all; format compact;
x=[-1, -1, 1;
2,  2, 1;
0,  0, 1;
 1,  1, 1;
-0.5, 0, 1;	
 2,  1, 1;	
 0,  1, 1;	
 3,  1, 1;	
 1,  2, 1;	
 3,  2, 1]; 

 d=[-1; 1;-1; 1; -1; 1; -1; -1; -1; 1];      
d
c=x'*d;
c
xx=x'*x;
xx
ix=inv(xx);
ix
w=ix*c;
w
%wi=0.5704./w
w=inv(x'*x)*x'*d
w=x\d