Write the Word or Phrase That Best Completes Each Statement $L=\left[\begin{array}{ccc}1 & m & n \\ p & q & r\end{array}\right]$

Essay

Write the word or phrase that best completes each statement or answers the question
-Using the matrix $L=\left[\begin{array}{ccc}1 & m & n \\ p & q & r\end{array}\right]$ , verify that $L+(-L)=O$ .