added calculation for simplify_product_function

src/main/py/read_math_function.py

@@ -103,3 +103,5 @@ def simplify_product_function(type, function):
         if not simplified_term or len(simplified_term) != 2:
             return False
         term_coefficient, term_variables = simplified_term
+        result_coefficient *= term_coefficient
+        result_variables += term_variables