%
% An upper triangular matrix whose inverse is very big 
% 
n = 10;
A = diag(ones(n,1)) + 2*diag(ones(n - 1, 1), 1);
b = zeros(n,1);
b(n) = 1;

A
y = backsubst2(A,b)

B = inv(A)

C = A'*A
CC = A*A'

D = inv(C)

E = inv(A')

F = inv(A)*inv(A')




