Question

If $A=\left[\begin{array}{ccc}1& -2& 1\\ 2& 1& 3\end{array}\right]B=\left[\begin{array}{cc}2& 1\\ 3& 2\\ 1& 1\end{array}\right]$ then $(AB{)}^{\prime }$ is equal to

• A. $\left[\begin{array}{cc}-3& -2\\ 10& 7\end{array}\right]$
• B. $\left[\begin{array}{cc}-3& 10\\ -2& 7\end{array}\right]$
• C. $\left[\begin{array}{cc}-3& 7\\ 10& 2\end{array}\right]$
• D. $\left[\begin{array}{cc}-3& 7\\ 10& -2\end{array}\right]$

Answer 1

Answer: (B)

$AB=\left(\begin{array}{cc}-3& -2\\ 10& 7\end{array}\right)$
$(AB{)}^T=\left(\begin{array}{cc}-3& 10\\ -2& 7\end{array}\right)$