diff --git a/Freitag/__pycache__/mathematik.cpython-39.pyc b/Freitag/__pycache__/mathematik.cpython-39.pyc
new file mode 100644
index 0000000..0e9b372
Binary files /dev/null and b/Freitag/__pycache__/mathematik.cpython-39.pyc differ
diff --git a/Freitag/check_env.py b/Freitag/check_env.py
new file mode 100644
index 0000000..474450a
--- /dev/null
+++ b/Freitag/check_env.py
@@ -0,0 +1,6 @@
+#start python umgebung 
+# python3 -m venv ~/pyenv
+# virtualenv ~/pyenv
+# virtualenv
+#source  ~/pyenv/activate
+#
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diff --git a/Freitag/db_insert.py b/Freitag/db_insert.py
old mode 100644
new mode 100755
diff --git a/Freitag/mathematik.py b/Freitag/mathematik.py
new file mode 100644
index 0000000..152a3e2
--- /dev/null
+++ b/Freitag/mathematik.py
@@ -0,0 +1,14 @@
+#/usr/bin/env python3
+
+
+def fak(n): 
+    if n == 0: 
+        return 1
+    if n < 0: 
+        raise ValueError("Fak ist eine negative Zahl")
+    if type(n) is not int:
+        raise TypeError("Fak ist keine ganze Zahl")
+    return n * fak(n-1)
+
+
+print(fak(4))
\ No newline at end of file
diff --git a/Freitag/test_fak.py b/Freitag/test_fak.py
new file mode 100644
index 0000000..396814f
--- /dev/null
+++ b/Freitag/test_fak.py
@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+from unittest import TestCase, main
+
+from mathematik import fak
+
+class FacultyTester(TestCase):
+    def test_basic(self):
+        self.assertEqual(fak(0), 1)
+        self.assertEqual(fak(1), 1)
+
+    def test_basic2(self):
+        self.assertTrue(fak(0) == 1)
+        self.assertTrue(fak(1) == 1)
+
+    def test_basic3(self):
+        self.assertFalse(fak(0) == 0)
+    
+    def test_greater(self):
+        for n in range(2,10):
+            self.assertGreater(fak(n), fak(n-1))
+    def test_invalid(self):
+        with self.assertRaises(Exception):
+            fak(-1)
+        with self.assertRaises(ValueError):
+            fak(-1)
+
+
+if __name__ == '__main__':
+    main()
+
+