diff --git a/chapter_appendix/math.md b/chapter_appendix/math.md
index 7d73f09b6ed6dca00b203fa8ec762bffb8a42565..2daa448c8bc6683b09be5b7fa3c4d92a956d0a8f 100644
--- a/chapter_appendix/math.md
+++ b/chapter_appendix/math.md
@@ -13,5 +13,3 @@ $$\nabla_\mathbf{x} f(\mathbf{x}) = \bigg[\frac{\partial f(\mathbf{x})}{\partial
 为表示简洁，我们有时用$\nabla f(\mathbf{x})$代替$\nabla_\mathbf{x} f(\mathbf{x})$。
 
 ### 泰勒展开
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