1> function y = avanti(L,b)
> y = b(1);
> for k = 2 : length(b)
> y = [y; b(k) - L(k, 1: k-1) * y];
> end
> end

2> L = [1 0 0; 2 1 0; -3 5 1]
L =

   1   0   0
   2   1   0
  -3   5   1


3> b = L * [4; -2; 7]
b =

    4
    6
  -15


4> avanti(L,b)
ans =

   4
  -2
   7


5> % dopo la lezione

5> function x = indietro(U,y)
> n = length(y);
> x = y(n)/U(n,n);
> for k = n-1 : -1 : 1
> x = [(y(k)-U(k,k+1 : n)*x)/U(k,k); x];
> end
> end

6> U = [-3 5 2; 0 4 -1; 0 0 7]
U =

  -3   5   2
   0   4  -1
   0   0   7


7> y = U * [4; -2; 7]
y =

   -8
  -15
   49


8> indietro(U,y)
ans =

   4
  -2
   7


9> quit