clear all
n=10;             %n=150,  something is incorrect. 

a = zeros(n,n);
for i=1:n
    for j=1:i-1
        a(i,j) = -1;
    end
    a(i,i)=1;

end


for i=1:n
    a(i,n)=1;
end

cond(a,inf)

% use computer to find l, u, and there inverse

[l, u] = lu(a);
ls
inv(l)
inv(u)
inv(a)