diff --git a/Book4_Ch01_Python_Codes/Bk4_Ch1_04.py b/Book4_Ch01_Python_Codes/Bk4_Ch1_04.py
deleted file mode 100644
index a9e05db..0000000
--- a/Book4_Ch01_Python_Codes/Bk4_Ch1_04.py
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@@ -1,26 +0,0 @@
-
-###############
-# Authored by Weisheng Jiang
-# Book 4  |  From Basic Arithmetic to Machine Learning
-# Published and copyrighted by Tsinghua University Press
-# Beijing, China, 2022
-###############
-
-# Bk4_Ch1_04.py
-
-import numpy as np
-
-# define two column vectors
-a = np.array([[-2], [5]])
-b = np.array([[5], [-1]])
-
-# calculate vector addition
-a_plus_b = a + b
-a_plus_b_2 = np.add(a,b)
-
-# calculate vector subtraction
-a_minus_b = a - b
-a_minus_b_2 = np.subtract(a,b)
-
-b_minus_a = b - a
-b_minus_a_2 = np.subtract(b,a)