diff --git a/pages/总复习2023t1.md b/pages/总复习2023t1.md
index 4d2109c..28b7980 100644
--- a/pages/总复习2023t1.md
+++ b/pages/总复习2023t1.md
@@ -2665,6 +2665,9 @@
 						- For every finite $$A1 , A2 , · · · , An$$,
 						  ![image.png](../assets/image_1686901672954_0.png)
 						- For every event A, $$P (A) = 1 − P (A)$$.
+						- If A ⊂ B, then P (B − A) = P (B) − P (A) and P (A) ⩽ P (B).
+						- For every two events A and B,
+						  $$P (A ∪ B) = P (A) + P (B) − P (AB)$$.
 						-
 					- Properties of Probability
 			- LATER 学积分