function [x]=fsub1(l,b)
%routine to solve the lower tringular matrix equation by 
% forward substitution
n=length(l);
for i=1:n
      x(i)=b(i);
      for j=1:i-1
         x(i)=x(i)-l(i,j)*x(j);
      end
      x(i)=x(i)/l(i,i);
end
x=x';
   