kr2

%Исходные данные
A = [10.8,0.0475,0,0;
    0.0321,9.9,0.0523,0;
    0,0.0369,9,0.057;
    0,0,0.0416,8.1;];

B = [12.143,13.0897,13.6744,13.8972];

%размер системы
N = max(size(B));

x = zeros(1,N);

v = zeros(1,N);
u = zeros(1,N);

%прямой прогон
v(1) = A(1,2) / (-A(1,1));
u(1) = (-B(1)) / (-A(1,1));

for i = 2:(N-1)
    v(i) = A(i,i+1) / (-A(i,i) - A(i,i-1)*v(i-1));
    u(i) = (A(i,i-1)*u(i-1) - B(i)) / (-A(i,i) - A(i,i-1)*v(i-1));
end;

v(N) = 0;
u(N) = (A(N,N-1)*u(N-1)-B(N)) / (-A(N,N) - A(N,N-1)*v(N-1));
% обратный прогон
x(N) = u(N);
for i = (N-1):-1:1
    x(i) = v(i) * x(i+1) + u(i);
end;

disp(x)