clear all, close all, clc

dd     = [2  3  3  2]';
d      = ones(5,1);
d(end) = -3;
A      = zeros(5);
A      = A + diag(dd, 1) + diag(d) + diag(dd, -1)

b  = [3  6  1  0  1]'
x  = A\b

db = 0.01*[-5  5  4  -3  -5]';
bs = b + db   % b stord
xs = A\bs   % x stord

xss = A\(1.02*b)   % Stör b likformigt och far missvisande kond
