function[A,b]=dreiecksform(A,b)
n=length(b);  
% In Dreiecksform umwandeln
for i=1:n-1
  for j=i+1:n
     if(A(i,i) == 0) 
		[A,b]=zeilentausch(A,b,1,2);
     end
            b(j) = b(j) - b(i)*A(j,i) / A(i,i);
            for k=i+1:n
                A(j,k) = A(j,k) - A(i,k)*A(j,i) / A(i,i);
            end
            for i=1:i
                A(j,i)=0;
            end
	end
end