% Linear Algebra: Theory and Applications
% Ward Cheney & David Kincaid
% JBPub.com (c) 2008 
% File: exp829a.m
% Example 8.2.9a Application: Linear Least-Squares Problem

A = [3.,2.; 1.,4.; 2.,1.]
b = [1.; 3.; 1.]
C = A'*A
d = A'*b
x = C\d

[Q, R] = qr(A)
x = R*Q'*b
e = A'*R