function [l,u] = F1(d,e,f)
m = length(d); l = zeros(m,1); u = zeros(m,1);
u(1) = d(1);
for i=2:m
    l(i) = e(i-1)/u(i-1);
    u(i) = d(i) - l(i)*f(i-1);
end
