diff --git "a/Chapitre 2 - Algebre matricielle/2.8-2.9 D\303\251composition LU (existance et algorithm).ipynb" "b/Chapitre 2 - Algebre matricielle/2.8-2.9 D\303\251composition LU (existance et algorithm).ipynb"
new file mode 100644
index 0000000..4ba73db
--- /dev/null
+++ "b/Chapitre 2 - Algebre matricielle/2.8-2.9 D\303\251composition LU (existance et algorithm).ipynb"	
@@ -0,0 +1,50 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# **Concept(s)-clé(s) et théorie**"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import Librairie.AL_Fct as al\n",
+    "import Corrections.corrections as corrections\n",
+    "from ipywidgets import interact_manual"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.7.4"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}
diff --git a/ToDo.md b/ToDo.md
index 683718a..41a1e8b 100644
--- a/ToDo.md
+++ b/ToDo.md
@@ -1,8 +1,8 @@
 ## Known problems to be fixed
 
 - [ ] *Plot3DSys* function has issues when the matrix has a rows made of all zeros
-- [ ] Exercise 4 in Notebook 1.2 displays a *RuntimeWarningError* due to a division by 0, 
+- [x] Exercise 4 in Notebook 1.2 displays a *RuntimeWarningError* due to a division by 0, 
       if the "sliding" parameter *h* is set to 0
-- [ ] *printA* library method fails if it is given a row vector (i.e. a list of int/float)
+- [x] *printA* library method fails if it is given a row vector (i.e. a list of int/float)
       as input
 - [ ] *ipywidgets* have troubles being displayed on **Noto**