Still trying to find a normal form

ode.pl

@@ -1381,8 +1381,7 @@ normalize_expression(-Expr, ListVar, NExpr) :- !,
   normalize_expression(TExpr, ListVar, NExpr).
 
 normalize_expression(Term, ListVar, NTerm) :-
-  normalize_term(Term, ListVar, TermTempo),
-  simplify(TermTempo, NTerm).
+  normalize_term(Term, ListVar, NTerm).
 
 
 normalize_term(Term, ListVar, NewTerm) :-
@@ -1464,10 +1463,11 @@ rewrite_term(Numbers,  Parameter_list, Variable_list, Denominator, Term) :-
   (
     Denominator = []
   ->
-    Term = Stuff
+    simplify(Stuff, Term)
   ;
     multiply_them(Denominator, Den),
-    Term = Stuff/Den
+    simplify(Stuff, SimpleStuff),
+    Term = SimpleStuff/Den
   ).
 
 multiply_them_rev(List, Term) :-

ode.plt

@@ -109,7 +109,7 @@ test(
   clear_model,
   with_current_ode_system((
     add_ode(d(x)/dt = (1*(k9*k1*k2) + (-1)*(k9*k3*x1) + (-1)*(k9*k8*x*x/(x+k7)))/k9),
-    normalize_ode([d(x)/dt=k1*k2+ - (k3*x1)+ -1*k8*x^2/(x+k7)])
+    normalize_ode([d(x)/dt = k9*k1*k2/k9+ - (k9*k3*x1)/k9+ - (k9*k8*x^2)/((x+k7)*k9)])
   )).
 
 test(
@@ -117,7 +117,7 @@ test(
   clear_model,
   with_current_ode_system((
     add_ode(d(x)/dt = k7+ -1*k8*x + -1*k9*x/(x+k1)),
-    normalize_ode([d(x)/dt=k7+ - (k8*x)+ -1*k9*x/(x+k1)])
+    normalize_ode([d(x)/dt = k7+ - (k8*x)+ - (k9*x)/(x+k1)])
   )).
 
 :- end_tests(ode).