function [x, lambda]=itinv(A, x, mu, tol, itmax)

x=x/norm(x);
for k=1:itmax
  y=(A-mu*eye(A))\x;
  y=y/norm(y);
  lambda=y'*A*y;
  if ( norm(y - lambda*x) < tol) then
    break
  end
  x=y;
end
endfunction

//n=10;
//A=2*diag(ones(n,1))-diag(ones(n-1,1),1)-diag(ones(n-1,1),-1);