## Quick Reference

Let **A** be a square matrix. The roots of the characteristic equation det(**A**−λ**I**)=0 are called the characteristic values of **A**. Then λ is a characteristic value of **A** if and only if there is a non-zero vector **x** such that **Ax**=λ**x**. Any vector **x** such that **Ax**=λ**x** is called a characteristic vector corresponding to the characteristic value λ.

*Subjects:*
Mathematics.