Find AB and BA.
-$A = \left[ \begin{array} { r r } 2 & - 2 \ - 3 & 9 \end{array} \right]$ and $B = \left[ \begin{array} { l l } 1 & 0 \ 0 & 1 \end{array} \right]$

A) $A B = \left[ \begin{array} { r r } 2 & - 2 \ - 3 & 9 \end{array} \right] ; B A = \left[ \begin{array} { r r } 2 & - 3 \ - 2 & 9 \end{array} \right]$

B) $A B = \left[ \begin{array} { l l } 2 & 0 \ 0 & 9 \end{array} \right] ; B A = \left[ \begin{array} { l l } 2 & 0 \ 0 & 9 \end{array} \right]$

C) $A B = \left[ \begin{array} { r r } 2 & - 2 \ - 3 & 9 \end{array} \right] ; B A = \left[ \begin{array} { r r } 2 & - 2 \ - 3 & 9 \end{array} \right]$

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

Question

Find AB and BA.
-$A = \left[ \begin{array} { r r } 2 & - 2 \ - 3 & 9 \end{array} \right]$ and $B = \left[ \begin{array} { l l } 1 & 0 \ 0 & 1 \end{array} \right]$

A) $A B = \left[ \begin{array} { r r } 2 & - 2 \ - 3 & 9 \end{array} \right] ; B A = \left[ \begin{array} { r r } 2 & - 3 \ - 2 & 9 \end{array} \right]$

B) $A B = \left[ \begin{array} { l l } 2 & 0 \ 0 & 9 \end{array} \right] ; B A = \left[ \begin{array} { l l } 2 & 0 \ 0 & 9 \end{array} \right]$

C) $A B = \left[ \begin{array} { r r } 2 & - 2 \ - 3 & 9 \end{array} \right] ; B A = \left[ \begin{array} { r r } 2 & - 2 \ - 3 & 9 \end{array} \right]$

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

Quizplus · Accepted Answer

Matrix B is the identity matrix, so multiplying it by matrix A (either AB or BA) leaves A unchanged.

Find AB and BA A=[2−2−39]A = \left[ \begin{array} { r r } 2 & - 2 \\ - 3 & 9 \end{array} \right]A=[2−3​−29​]

Find AB and BA $A = \left[ \begin{array} { r r } 2 & - 2 \\ - 3 & 9 \end{array} \right]$