function result=HW14_5(A,B,C,b)

n = length(A);
D = zeros(1,n);
E = zeros(1,n-1);
F = zeros(1,n-1);

%Solve Lz=b
z = zeros(1,n);
D(1) = A(1);
F(1) = C(1)/D(1);
z(1) = b(1)/D(1);

for i = 1:n-2
  E(i) = B(i);
  D(i+1) = A(i+1) - E(i)*F(i);
  F(i+1) = C(i+1)/D(i+1);
  z(i+1) = (b(i+1)-E(i)*z(i)) / D(i+1);
end

E(n-1) = B(n-1);
D(n) = A(n)-E(n-1)*F(n-1);
z(n) = (b(n)-E(n-1)*z(n-1))/D(n);

%Solve Ux=z
x = zeros(1,n);
x(n) = z(n);

for i=n-1:-1:1
  x(i) = z(i) - F(i)*x(i+1);
end

result = x;

end