function Feb14()

n = 5;
% An easy positive definite symmetric matrix..
A = pascal(5);
% Its Cholesky factor...
G = chol(A,'lower')
% Compare the (1,1) blocks in the equation
%  [A(1:n-1,1:n-1) A(1:n-1,n) ; A(n,1:n-1) A(n,n)] =
%  [G(1:n-1,1:n-1) zeros((1:n-1,1) ; G(n,1:n-1) G(n,n)]* 
%  [G(1:n-1,1:n-1) zeros((1:n-1,1) ; G(n,1:n-1) G(n,n)]'
Err = A(1:n-1,1:n-1) - G(1:n-1,1:n-1)*G(1:n-1,1:n-1)'
b = randn(n,1);
x = G'\(G\b);
Twoxs = [x A\b]
y = G(1:n-1,1:n-1)'\(G(1:n-1,1:n-1)\b(1:n-1));
Twoys = [y A(1:n-1,1:n-1)\b(1:n-1)]