Fie [tex]A=\left([tex]\begin{array}{rrr}1 & -1 & 1 \\ -1 & 1 & 1 \\ 1 & 1 & -1\end{array}\right), B=\left(\begin{array}{lll}1 & 0 & 1 \\ 0 & 1 & 0 \\ 1 & 0 & 1\end{array}\right)[/tex]. Calculați [tex]A B, B A, A B-B A, \mathrm{Tr}(A B-B A)[/tex] şi deduceți că [tex]A B-B A \neq I_{3}\space [/tex].[/tex]