diff --git a/polimani.pl b/polimani.pl
index d52d542..b686116 100644
--- a/polimani.pl
+++ b/polimani.pl
@@ -581,3 +581,17 @@ scale_polynomial(P, C, S) :-
 %% Tests:
 %% ?- scale_polynomial(3*x^2, 2, S).
 %@ S = 2*3*x^2.
+
+%% add_polynomial(+P1:polynomial,+P2:polynomial,-S:polynomial) is det
+%
+%  S = P1 + P2
+%
+add_polynomial(P1, P2, S) :-
+    polynomial_to_list(P1, L1),
+    polynomial_to_list(P2, L2),
+    append(L1, L2, LA),
+    join_like_terms(LA,LJ),
+    list_to_polynomial(LJ, P),
+    simplify_polynomial(P, S).
+%% Tests:
+%