function x = GaussFaraPiv( A, b )
%UNTITLED5 Summary of this function goes here
%   Detailed explanation goes here
n = length(b);
A_ext = [A,b];
for k = 1:n-1
	p = find(A_ext(k:n, k)~=0,1,'First');
	if(isempty(p) == 1
		disp('sist este incompatibil/comp nedet');
		x=[];
		return;
	end
	p = p+k-1;
	if p>k
		A_ext([p,k],:)=A_ext([k,p],:);
	end
	for l = k-1:n
		m(l,k) = A_ext(l,k)/A_ext(k,k);
		A_ext(l,:) = A_ext(l,:)-m(l,k)*A_ext(k,:);
	end
	if A_ext(n,n) == 0
		disp('...');
		x=[];
		return;
	end
end
end



%%function x = MetSubstDesc( A, b )
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here
n = length(b); %n = size(A,1), n=size(A,2)
x = zeros(n,1);
x(1) = b(1)/A(1,1);
for k = n-1:1
	%eventual cu suma/for
	%sau:
	x(k) = ( b(k) - A(k,k+1:n)*x(k+1:n) )/A(k,k);
end

end


%%
function x = MetSubstAsc( A, b )
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here
n = length(b); %n = size(A,1), n=size(A,2)
x = zeros(n,1);
x(1) = b(1)/A(1,1);
for k = 2:n
	%eventual cu suma/for
	%sau:
	x(k) = ( b(k) - A(k,1:k-1)*x(1:k-1) )/A(k,k);
end

end