Find AB and BA.
-$A = \left[ \begin{array} { l l l } 1 & 0 & 0 \ 0 & 1 & 0 \ 0 & 0 & 1 \end{array} \right]$ and $B = \left[ \begin{array} { r r r } 1 & 1 & - 5 \ 8 & - 9 & - 5 \ - 1 & 4 & 5 \end{array} \right]$

A) $A B = \left[ \begin{array} { r r r } 1 & 1 & - 5 \ 8 & - 9 & - 5 \ - 1 & 4 & 5 \end{array} \right] ; B A = \left[ \begin{array} { r r r } 1 & 8 & - 1 \ 1 & - 9 & 4 \ - 5 & - 5 & 5 \end{array} \right]$

B) $A B = \left[ \begin{array} { r r r } 1 & 0 & 0 \ 0 & - 9 & 0 \ 0 & 0 & 5 \end{array} \right] ; B A = \left[ \begin{array} { r r r } 1 & 0 & 0 \ 0 & - 9 & 0 \ 0 & 0 & 5 \end{array} \right]$

C) $A B = \left[ \begin{array} { l l l } 1 & 0 & 0 \ 0 & 1 & 0 \ 0 & 0 & 1 \end{array} \right] ; B A = \left[ \begin{array} { l l l } 1 & 0 & 0 \ 0 & 1 & 0 \ 0 & 0 & 1 \end{array} \right]$

D) $A B = \left[ \begin{array} { r r r } 1 & 1 & - 5 \ 8 & - 9 & - 5 \ - 1 & 4 & 5 \end{array} \right] ; B A = \left[ \begin{array} { r r r } 1 & 1 & - 5 \ 8 & - 9 & - 5 \ - 1 & 4 & 5 \end{array} \right]$

Question

Find AB and BA.
-$A = \left[ \begin{array} { l l l } 1 & 0 & 0 \ 0 & 1 & 0 \ 0 & 0 & 1 \end{array} \right]$ and $B = \left[ \begin{array} { r r r } 1 & 1 & - 5 \ 8 & - 9 & - 5 \ - 1 & 4 & 5 \end{array} \right]$

A) $A B = \left[ \begin{array} { r r r } 1 & 1 & - 5 \ 8 & - 9 & - 5 \ - 1 & 4 & 5 \end{array} \right] ; B A = \left[ \begin{array} { r r r } 1 & 8 & - 1 \ 1 & - 9 & 4 \ - 5 & - 5 & 5 \end{array} \right]$

B) $A B = \left[ \begin{array} { r r r } 1 & 0 & 0 \ 0 & - 9 & 0 \ 0 & 0 & 5 \end{array} \right] ; B A = \left[ \begin{array} { r r r } 1 & 0 & 0 \ 0 & - 9 & 0 \ 0 & 0 & 5 \end{array} \right]$

C) $A B = \left[ \begin{array} { l l l } 1 & 0 & 0 \ 0 & 1 & 0 \ 0 & 0 & 1 \end{array} \right] ; B A = \left[ \begin{array} { l l l } 1 & 0 & 0 \ 0 & 1 & 0 \ 0 & 0 & 1 \end{array} \right]$

D) $A B = \left[ \begin{array} { r r r } 1 & 1 & - 5 \ 8 & - 9 & - 5 \ - 1 & 4 & 5 \end{array} \right] ; B A = \left[ \begin{array} { r r r } 1 & 1 & - 5 \ 8 & - 9 & - 5 \ - 1 & 4 & 5 \end{array} \right]$

Quizplus · Accepted Answer

Matrix $A$ is the identity matrix, so $AB = B$ and $BA = B$. Multiplying any matrix by the identity matrix leaves it unchanged.

Find AB and BA A=[100010001]A = \left[ \begin{array} { l l l } 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{array} \right]A=​100​010​001​​

Find AB and BA $A = \left[ \begin{array} { l l l } 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{array} \right]$