diff --git a/mapytex/calculus/API/__init__.py b/mapytex/calculus/API/__init__.py
index f5b120e..1502cdf 100644
--- a/mapytex/calculus/API/__init__.py
+++ b/mapytex/calculus/API/__init__.py
@@ -117,7 +117,7 @@ x^7
 (2x - 3)(- x + 2)
 (2x - 3)(- x + 2)
 2x(- x) + 2x * 2 - 3(- x) - 3 * 2
-2 * - 1 * x^(1 + 1) + 2 * 2 * x - 3 * - 1 * x - 6
+2(- 1) * x^(1 + 1) + 2 * 2 * x - 3(- 1) * x - 6
 4x + 3x - 2x^2 - 6
 (4 + 3) * x - 2x^2 - 6
 - 2x^2 + 7x - 6
diff --git a/mapytex/calculus/core/renders/tree2tex.py b/mapytex/calculus/core/renders/tree2tex.py
index 531c08b..ae09150 100644
--- a/mapytex/calculus/core/renders/tree2tex.py
+++ b/mapytex/calculus/core/renders/tree2tex.py
@@ -91,9 +91,11 @@ def mul2tex(left, right):
     '- 3x'
     >>> mul2tex(a, a)
     'x \\times x'
+    >>> mul2tex(a, MO.factory(-3))
+    'x(- 3)'
     """
     left_ = render_with_parenthesis(left, "*")
-    right_ = render_with_parenthesis(right, "*")
+    right_ = render_with_parenthesis(right, "*", is_at_right=True)
 
     display_time = True
     # if (right_[0].isalpha() and (left_.isnumeric() or left_.isdecimal())) or right_[
@@ -183,23 +185,17 @@ def pow2tex(left, right):
     return f"{left_}^{{{right_}}}"
 
 
-def render_with_parenthesis(subtree, operator):
+def render_with_parenthesis(subtree, operator, is_at_right=False):
     subtree_need_parenthesis = False
     try:
         subtree.node
     except AttributeError:
-        try:
-            if (
-                OPERATORS[subtree.MAINOP]["precedence"]
-                < OPERATORS[operator]["precedence"]
-            ):
-                subtree_need_parenthesis = True
-        except (AttributeError, KeyError):
-            pass
         try:
             subtree_ = subtree.__tex__
         except AttributeError:
             subtree_ = str(subtree)
+        if subtree_.startswith("-") and OPERATORS["-"]["precedence"] < OPERATORS[operator]["precedence"] and is_at_right:
+            subtree_need_parenthesis = True
     else:
         if OPERATORS[subtree.node]["precedence"] < OPERATORS[operator]["precedence"]:
             subtree_need_parenthesis = True
diff --git a/mapytex/calculus/core/renders/tree2txt.py b/mapytex/calculus/core/renders/tree2txt.py
index 2942d9e..d46a11e 100644
--- a/mapytex/calculus/core/renders/tree2txt.py
+++ b/mapytex/calculus/core/renders/tree2txt.py
@@ -91,11 +91,13 @@ def mul2txt(left, right):
     '- 3x'
     >>> mul2txt(a, a)
     'x * x'
+    >>> mul2txt(a, MO.factory(-3))
+    'x(- 3)'
     """
     display_time = True
 
     left_ = render_with_parenthesis(left, "*")
-    right_ = render_with_parenthesis(right, "*")
+    right_ = render_with_parenthesis(right, "*", is_at_right=True)
 
     if right_[0].isalpha():
         # TODO: C'est bien beurk en dessous... |ven. déc. 21 12:03:07 CET 2018
@@ -187,23 +189,22 @@ def pow2txt(left, right):
     return f"{left_}^{right_}"
 
 
-def render_with_parenthesis(subtree, operator):
+def tree_with_parenthesis(subtree, operator):
+    """ Assuming the subtree is a tree, then have .node """
+    pass
+
+
+def render_with_parenthesis(subtree, operator, is_at_right=False):
     subtree_need_parenthesis = False
     try:
         subtree.node
     except AttributeError:
-        try:
-            if (
-                OPERATORS[subtree.MAINOP]["precedence"]
-                < OPERATORS[operator]["precedence"]
-            ):
-                subtree_need_parenthesis = True
-        except (AttributeError, KeyError):
-            pass
         try:
             subtree_ = subtree.__txt__
         except AttributeError:
             subtree_ = str(subtree)
+        if subtree_.startswith("-") and OPERATORS["-"]["precedence"] < OPERATORS[operator]["precedence"] and is_at_right:
+            subtree_need_parenthesis = True
     else:
         if OPERATORS[subtree.node]["precedence"] < OPERATORS[operator]["precedence"]:
             subtree_need_parenthesis = True