diff --git a/linear-algebra/knowledge/2-matrix/matrix.pdf b/linear-algebra/knowledge/2-matrix/matrix.pdf
index 67c66d1..77d99b9 100644
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diff --git a/linear-algebra/knowledge/2-matrix/matrix.tex b/linear-algebra/knowledge/2-matrix/matrix.tex
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--- a/linear-algebra/knowledge/2-matrix/matrix.tex
+++ b/linear-algebra/knowledge/2-matrix/matrix.tex
@@ -381,4 +381,6 @@ $$A^*=\left(
 
 \section{逆矩阵}
 
+逆矩阵类比倒数，若对于$n$阶矩阵$A$，有一个$n$阶矩阵$B$，使得$AB=BA=E$，则$A$可逆，$B$是$A$的逆矩阵也称为逆阵，且逆矩阵唯一，记为$B=A^{-1}$。
+
 \end{document}