n=800;
alpha=1;
A=zeros(n,n);
for i=1:n-1
    A(i,i)=2+alpha;
    A(i+1,i)=-1;
    A(i,i+1)=-1;
end
A(n,n)=2+alpha;
b=zeros(n,1);b(1)=1;
x=A\b;
[z,theta]=compito(n,alpha);
xhat=[z/theta;1/theta];
norm(x-xhat,inf)/norm(x,inf)