How To Study As A Mathematics Major
《How To Study As A Mathematics Major》 · 第 49 页 · Section 1.2「Eigenvalues, eigenvectors, and similarity」，Definition 1.2.3
Thought of as a formal polynomial in $t$, the characteristic polynomial of $A\in M_n$ is $p_A(t)=\det(tI-A)$. We refer to the equation $p_A(t)=0$ as the characteristic equation of $A$.